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April 10, 2019
The last articles walked you through renewable energy systems in housing:
General principles of renewable energy
Passive solar design
On-site renewable energy systems (solar thermal, photovoltaics, wind and microhydro)
This article introduces the concept of high performance houses, and takes a high-level view of strategies and approaches to achieving high performance houses. Two more articles are in the works to focus on High Performance, one for new construction and one for improving existing houses.
Here’s the evaluation form, so you can rate yourself on your existing understanding of Strategies and Approaches to High Performance Housing. The rating is from 0 (I know nothing about this topic) to 4 (I’m an expert in this topic and can handle complex tasks on the daily). You don’t have to share this with anyone else, so rate yourself honestly!
Why High Performance Housing?
There are many benefits to high performance housing. Energy Benefits like reduced operating costs are obvious, but there are some excellent benefits that tag along with energy conservation measures.
Homeowners consistently rank comfort, health and safety higher than energy savings in studies that ask why they undertook energy conservation measures in their homes.
Environmental benefits also often rank higher than energy savings in studies of homeowner drivers. Reducing fossil fuel use and greenhouse gas emissions get highest rankings, but water conservation measures and the idea that a well-built house or a repurposed/retrofitted house, using carefully selected materials, is a good way to protect resources. Resource protection can take the form of recycled or recyclable materials, wood and wood products that carry a certificate of sustainable growth, harvest, and manufacture, for example.
Financial benefits are, surprisingly, lower-ranking in most homeowner studies than energy, non-energy and environmental benefits. Real or perceived higher up front costs can keep some people away from energy efficiency in new housing. It’s hard to get people to think in terms of the long run, and how lower operating costs will help them when they are confronted with a high price.
But the financial benefits of the long term low operating costs are very real. Obviously a cost-effectiveness analysis needs to be carried out to ensure that this is the case.
Energy Benefits for Homeowner/Occupant
Reduced operating costs
More resiliency in extreme weather
Overall Occupant Benefits
Increased comfort level year round
Improved occupant health and safety
Quieter indoor living
Durability & longevity of structure
Less reliance on fossil fuels
Reduced greenhouse gas emissions
Water conservation measures
Protection of resources
Economic Benefits (homeowner)
Lower long-term operating costs
Higher resale value (future)
Economic Benefits (industry)
Code improvements lead to consistency across jurisdictions
More competition can create new economic development
Local Government Benefits
Achieve climate-action goals
Improve community resilience
Reduce energy poverty/Improve energy security
What is High Performance Housing?
While there is no specific definition of a ‘high performance house’, generally the term has come to describe a house or building where the designers, builders, and owners have set a higher bar than code compliance for:
Indoor air quality
Lower energy use
High performance housing is a term that is used to describe an energy efficient or sustainable building that is not affiliated with any particular program or target.
There are six primary High Performance Housing goals and features:
Control Air Leakage
Increase Insulation Levels
Minimize Thermal Bridging
Place/Size Doors and Windows Strategically
Provide Balanced Mechanical Ventilation
Right-size Space Conditioning and DHW Equipment
There are many other terms that are used to describe houses that are built or renovated to a standard that is beyond current building code compliance. They often are associated with a program that focuses on energy reduction targets, such as low energy, low impact, net zero, net carbon, sustainable, green, living building. The most important goal, regardless of the term or label used, is very straightforward:
Reduce the overall energy load of the building.
Fundamentally, you cannot have a sustainable building if it does not address energy efficiency first and foremost. However, sustainability is more than just energy efficiency –issues like water efficiency needs to be addressed. Material choices are also a big part of sustainability: Are they recycled or recyclable? Are they local or regionally produced? Are they healthy choices for occupants?
Reducing the overall load of the building includes space conditioning (heating and cooling, mechanical ventilation, and dehumidification in some climates) domestic hot water and occupant loads (lighting, appliances, electronics).
Space conditioning is the biggest portion of energy consumption in a building. The first line of attack is improving the building envelope, the permanent aspects of the building. We do this by reducing air leakage and increasing the thermal envelope to minimize the heat loss and the heat gain loads required to keep the house comfortable. This means smaller capacity equipment and lower annual energy costs.
Building envelope upgrades to new construction or retrofit projects, carried out according to best practices, ensure that occupant comfort and health as well as building durability are enhanced.
Indoor air quality and a healthy indoor environment were not as much of an issue a couple of generations ago, in part, because people typically spent much more time outdoors. Now, most North Americans are indoors more than 90% of the time.
At the same time that we have moved indoors, we have also developed materials and products for indoor environments that have a negative effect on indoor air quality. Materials and products offgas volatile organic compounds (VOCs) – think of the smell of new carpet, paint or air freshener -- and formaldehyde, which you can’t smell. Fine particulate matter, associated with combustion products and urban haze, is also a growing concern. Anything with a diameter of 2.5 microns or less (known as PM 2.5), penetrates deeply into the alveolar region of the lung and may even be able to cross into the blood, affecting the functioning of the lungs and the heart.
With this in mind, we want to ensure that the materials and products that are used in construction and finishing high performance houses are not increasing the pollutant load in the house and therefore causing occupant health concerns because of poor indoor air quality.
There are many ways to optimize domestic hot water and occupant loads. Unlike the building envelope, these loads are driven by occupant behaviour, number of occupants, and lifestyle. Hard to anticipate and control, so we look at ways of optimizing them. You can take a deep dive into those areas by reading these blog articles:
When we improve the building envelope, we reduce the overall amount of energy required to keep the house comfortable for the occupants. Some programs look at reductions of 20, 50, or 80 percent reduction in energy use from current code compliance. So the overall ‘pie’ of energy required by the house gets smaller. A high performance house that is 50 to 80 percent better than code not only has a smaller energy consumption pie, the proportions of energy end use changes. The table shows the effect a high performance building envelope has on where and how energy is used in a house.
Code Compliant House/Existing House
High Performance House
Domestic Hot Water
This changes how you approach providing DHW and space conditioning.
Minimizing the energy inputs for the house has a ripple effect that keeps spreading as the years go on: reduced ongoing site environmental damage and pollution from fossil fuel consumption, reduced resource extraction, reduced peak capacity requirements and improved load balancing for utilities, more cost-effective infrastructure for cities and towns.
Energy Efficient House: a house consumes (and wastes) the minimum amount of energy possible (based on budgetary constraints, material/equipment availability, builder capability, owner passion) while maintaining comfort levels for the occupants.
Net Zero Energy House: a NZE house produces as much renewable energy in a year as the purchased energy it consumes. Some states, provinces and cities have already put NZE target dates into legislation — for example, by 2020, all new houses in California must be NZE. British Columbia has instigated an Step Energy Code to bring houses to NZE by 2032. The Canadian Home Builder’s Association (CHBA) has a Net Zero Energy labelling program that requires a 33% reduction in thermal energy demand below a code-compliant base case.
Net Zero Energy Ready: (NZE-r) A house that has been optimized for NZE, but does not have the renewable energy system installed. The National Model Building Code of Canada will require new buildings to meet NZE-r by 2030.
Zero Carbon House: A house that has zero net energy emissions. Carbon emissions generated by onsite or off site fossil fuel use are balanced by the amount of onsite renewable energy production. This is a more established concept in the UK than in North America, however, the Canadian Green Building Council announced a Net Zero Carbon Building Standard in 2018.
Sustainable House: a house that uses energy and material effectively and efficiently during construction AND in operation, creating as little damage and pollution to natural systems as possible throughout its lifecycle.
Net Zero Energy - It’s coming to a building code near you!
It’s simply a target for balancing out the equation:
Energy in = Energy out
The amount of energy consumed by the building is offset by the energy it generates on site. Typically, this means photovoltaic (PV) panels.
In theory, any building can be a net-zero energy building, if it has enough site-generated energy. However, the best approach to net-zero is one that starts with energy conservation measures, just like any other high-performance building:
Reduce the demand for energy: this means a highly insulated and airtight building enclosure with heat recovery ventilation
Optimize energy through high-performance mechanical systems and equipment, and low-energy lighting and appliances.
Generate the balance of energy through renewable supply like PV.
Under the bare bones definition of the concept, Net Zero Energy does not take into account things like carbon loads and greenhouse gas emissions for the energy that the building consumes, nor does it require water conservation, sustainable materials choices or any environmental responsible practices.
A house that meets the NZE target may not address anything other than energy efficiency, missing the boat on long-term sustainability. On the other hand, a sustainable building that incorporates green material choices, water conservation, site planning, occupant health and broader planning issues, but addresses actual energy efficiency in the most minimal way, also misses the boat on long-term sustainability.
To improve the building envelope and reduce space conditioning loads, it’s all about control. Controlling heat, air, and moisture flows. To do this, we look at the three control layers that all high performance houses need.
What are the three main control layers for heat, air, and moisture flows?
The building envelope, the skin and bones of the house, is where we have the opportunity to reduce energy consumption for both heating and cooling. The building envelope is the permanent part of the house. Choices about insulation levels, air sealing techniques, window and door characteristics, and exterior finishes are crucial to the durability, longevity, and long-term affordability of a house.
The building envelope needs three key items to perform well from a building science perspective:
A vapour barrier, or vapour diffusion retarder, to keep moisture vapour from the house from entering the wall cavity.
An air barrier, to stop accidental air movement (infiltration and exfiltration, the stack effect).
A thermal blanket to reduce the flow of heat transfer from inside to outside.
Controlling heat, air, and moisture flows layers also helps to achieve and maintain a healthy indoor environment, including the control of:
Indoor Air Quality
Reducing Heating and Cooling Loads
Heating and cooling loads are reduced by improving the thermal barrier and ensuring that air change rates are minimized by using a continuous air barrier. Heat loss and heat gain calculations are important for all houses, but imperative for right-sizing equipment in high-performance houses.
A successful strategy for a high performance building envelope includes four primary goals:
Lower air change rates
Minimal thermal bridging
Avoidance of dew point/condensation in assemblies
Current construction practices vary across Canada, but here is a comparison between typical insulation values and target insulation values for NZE houses in cold climates, as well as window choices and target air leakage rates.
Net Zero Energy Target
R30 to R40
R60 to R80
Above Grade Wall
R20 to R24
R35 to R40
R30 to R40
R60 to R80
Below Grade Wall
R12 to R24
R32 to R40
Energy Star® Double Pane
2.5 to 4.5 ACH@50Pa
Determining R-values of Construction Assemblies
A quick recap:
Conduction is the transfer of energy through a solid OR between touching materials.
Conductivity is the rate of heat flow through materials. A good conductor has high conductivity, and allows heat to flow easily, a good insulator has low conductivity, and slows the rate of heat flow.
Conductance, U-factor, is a value given to a specific material. It describes the conductivity per unit of thickness of the material.
Low conductivity materials lower the overall conductance of building assemblies. However, U-factors are not user-friendly numbers. They can’t be added together, they represent the building assembly, not the individual materials that make up the assembly. To make things easier when doing calculations, we use the inverse of conductance, thermal resistance, known as the R-value. Mathematically, it looks like this:
If U-factor of an assembly is 0.05, then
1 divided by 0.05 equals 20. The R-value is 20.
R-values can be added together, but you cannot do more complicated math with them, so for some applications, the R-value might have to be translated back to a U-factor, using the equation:
U-factor (metric): W/(m2*K) Where W = Watts and K= degrees Kelvin
R-value (imperial): °F*ft2*sec/BTU
RSI (metric): °C*m2*sec/Joule
Mathematically, R-value is calculating from a measuring heat flow across a surface where each side is at a particular temperature:
ΔT (called ‘delta T’) is the temperature difference inside and outside the house in °F (or °C for RSI)
Area is the area of the wall (or ceiling) that's being insulated in ft 2 (or m2 for RSI)
Time is how long the measurement took place in seconds (same in RSI)
HeatLoss is how much heat is lost through the wall in BTU (J in RSI)
To convert from metric to imperial:
R = 5.678 * RSI
Nominal vs. Effective R-values
Just to make things a little more complicated, R-values are not always what they seem. There is the tested thermal resistance of a material, the number you can see stamped on a batt for example, and there is the R-value of a whole assembly, including framing.
Nominal: the tested R-value of an insulation material. When we are talking about an ‘R20’ wall, it’s shorthand for a wall that has R20 batts in the cavity.
Effective: the overall resistance of the assembly, including all components and materials, indoor and outdoor air films, and the effect of thermal bridging. That ‘R20’ wall? It’s effective R-value is based on the actual construction of the wall. Recall that thermal bridging is heat loss that occurs when there are materials of different conductivity. For example, a wall built of 2x6 studs at 16 o.c., that has an R20 batt in the wall cavity. Every 16”, the conductivity of the wall is reduced to R5.5, because wood is about R1 per inch of thickness. If the wall has wood siding, a rainscreen detail, OSB sheathing and an interior air/vapour barrier with drywall finish on the interior, the effective R-value of that wall is a total of the following layers.
Material or Layer
Exterior air film
¾” Air Space
½” OSB sheathing
R20 fiberglass batt
6 mil poly
Interior air film
Total R-values for wall system
But this R-value is only true of the cavity areas. The framed portion of the wall is:
R24.1 - R20 = R4.1, the R-value of the assembly without the fiberglass.
R4.1 + R1*5.5inches = R9.6, the R-value of the framing portion.
The framing can account for 10 to 20 percent of the exposed wall surface, so the effective R-value could be significantly lower than the nominal.
Using our 2x6 wall @ 16” oc with R20 batts in the cavity, assume that with studs, plates and framing at rough stud cavities, the framing is 15% of the total wall surface.
To get the effective R-value, you can do an area-weighted calculation, or you can use thermal modelling software. There are some good calculators out there. The Canadian Wood Council’s calculator has a large catalogue of wall types and puts it in your climate zone. It is regularly updated. Here’s the link to the Reff: effective R-value calculator. This takes all the guesswork, and a lot of the learning curve out of your hands. From the CWC website:
“The calculation of effective thermal resistance is performed in compliance with NBC Sub-section 9.36.5. of Division B.
Each assembly comes with a climate-specific colour-coded durability assessment, which has been determined considering computer analysis and field experience by building science experts in Canada.”
Area-weighted Effective R-value Calculation
To understand the area-weighted calculation process, here’s how to do it using the example of the ‘R20’ wall above.
You must divide the % area occupied by each R-value by the R-value itself, add them together to get a total, and then divide 100 by that total.
That formula looks like this:
100/((% area framing divided by R-framing)+(% area insulation divided by R-insulation)
The math goes like this:
Step 1: 85% of the wall is R24.1: 85/24.1=3.52
Step 2: 15% is R9.6 = 15/9.6=1.56
Step 3: 3.52 + 1.56 = 5.08
Step 4: 100/5.08 = 19.68
The effective R-value is R19.68
But does this pass Code?
To add even more complexity, the Code is in metric. AND the prescriptive path requirement for overall thermal transmittance (in U-factor) of assemblies. This is the inverse of the effective resistance (R-value) of the assembly.
To find out if this wall meets code requirements, first change R-value to RSI:
R19.68/5.678 = 3.47 RSI
U-factor = 1/RSI = 1/3.47 = 0.288 (the units are W/m2*K)
Table 188.8.131.52 of the building code, Overall Thermal Transmittance of Above Ground Opaque Building Assemblies shows a range of maximum U values for walls in different climate zones in Canada. Remember, R-value measures resistance to heat transfer. The higher the R-value, the better the resistance to heat transfer. U-value measures the rate of heat transfer. The lower the U-value, the better the resistance to heat conduction. That’s why the values in Table 184.108.40.206 are shown as ‘maximum’ values for Overall Thermal Transmittance.
Our wall, with 0.288 meets the prescriptive path only in Zone 4, where the maximum allowable value for walls is 0.315.
Here is a comprehensive table of Insulation Values from Inspectapedia.
Energy Use Metrics
Energy Use Intensity (EUI)
Energy Use Intensity (EUI) is the amount of energy used per square foot or meter of conditioned (heated and/or cooled) space in a building. It has been compared to the fuel efficiency rating on cars in litres per 100 km or miles per gallon. It’s a way of comparing the energy use of different buildings regardless of size or shape. EUI is measured in Imperial or US units as kBtu/sf * year. The EnerGuide for Houses label shows EUI in kWh/m2 * year.
The lower the EUI, the better the performance of a building.
Energy Use Intensity (EUI) is primarily used to describe the building’s total modeled annual energy consumption including heating, cooling, ventilation, plus lighting and plug load energy for larger residential (Part 3) buildings.
Thermal energy demand intensity (TEDI)
Thermal energy demand intensity (TEDI) is a metric that describes the annual net heat loss for a building. TEDI accounts for heat losses from the building envelope (thermal and air tightness levels) and the ventilation system. It also accounts for all passive heat gains (solar, occupant, appliance and equipment). TEDI targets are useful when determining ways to minimize the heating load of a house so that renewable energy systems can be optimized. A highly insulated, airtight house with an HRV will have a lower (better TEDI) value than a house that has minimal insulation, a high air leakage rate and no heat recovery.
In the BC Energy Step Code, TEDI threshold values and air tightness testing are required to meet various steps in various climatic regions. For example, for Part 9 buildings, blower door test results must be within 3.0 ACH50 for Step 2, but a house designed to meet Step 5 must have blower door test that comes in at 1.0ACH50 or less.
Mechanical Energy Use Intensity (MEUI)
MEUI is used in the BC Energy Step Code, and is similar to EUI, but tailored to Part 9 buildings. MEUI measures the modelled energy use for space conditioning, ventilation and domestic hot water per square metre of conditioned space per year. It does not include lighting and appliance/electronic/plug loads, as EUI does. This is because occupant behaviour is very different across households, where in Part 3 buildings, there are more consistent lighting loads and appliance loads can be averaged.
The Passive House program uses similar metrics for heating demand (TEDI) and primary energy use (EUI).
Building Science Corporation article on Performance Metrics
Codes and Energy Efficient Housing
The National Building Code of Canada (NBC) is published by the National Research Council as a ‘model code’ for adoption (in whole or part) by provincial and municipal governments, as the Constitution of Canada deems that regulating building construction is a provincial responsibility. However, in 1941, the NBC came into existence and was adopted by most provinces and municipalities within the next 20 years. The building code, as well as other codes that affect residential construction, are developed by the Canadian Commission on Building and Fire Codes and are updated on a 5 year cycle. More details and history can be found in this Wikipedia entry.
Residential construction falls under Part 9 of the National Building Code of Canada (NBC). Part 9 covers houses and small residential buildings that have:
3 above-ground storeys or less
A building area no more than 600 square metres
This includes single detached dwellings, duplexes, townhouses, and small apartment buildings.
Like other building codes, the NBC is primarily concerned with health, safety, accessibility and the protection of buildings from fire or structural damage. The Code applies to new construction, demolition, relocation, some aspects of renovation and change of building use. Energy efficiency requirements were added to the Code in the 2010 cycle and published in a new section containing energy efficiency requirements for housing and small buildings in December 2012. There will be a model Renovation Code in place by 2022, and the NBC will require new construction to be NZE-ready by 2030.
The Energy Code for residential construction falls under Part 9.36 of the NBC. The National Energy Code of Canada for Buildings (NEBC) is broken into three divisions:
Division A- Compliance, Objectives, and Functional Statements
This section Provides the following basis for the code:
Definitions and terms
Functional statements to meet that objective
Division B- Acceptable Solutions
This section makes up the bulk of the code, and provides the requirements, provisions and design guidelines for code compliance.
Part 1: General
Part 3: Building Envelope
Part 4: Lighting
Part 5: Heating, Ventilating, and Air-conditioning Systems
Part 6: Service Water Heating Systems
Part 7: Electrical Power Systems and Motors
Part 8: Building Energy Performance Compliance Path
Division C- Administrative Provisions
How to document and prove that all requirements are met
Details on alternative solutions
Descriptions of possible exemptions
You can now get online access to the National Building Code and the National Energy Code for free. Use this link to register for an account. You can download a copy as pdf, or you can use your browser online.
There are three ways to build new houses to be compliant with Part 9 of the Code (provincial codes follow the same structure as the NBC).
One is the prescriptive path, which requires minimum insulation levels in the various components of the house. There are tables that show one or more paths to meeting the code requirements, and you must comply with one path completely. Some provinces have several prescriptive paths, depending on how many climate zones they encompass. A second way is the trade-off path, which allows for some substitutions or trade offs between different components. The third way to meet the building code is the performance path, which allows the designer or builder to trade off insulation and air tightness with high-performance equipment. This means there is no right or wrong way to construct the house. The house must meet an energy target, but how that is done is up to the designer or builder. This gives much more flexibility than the prescriptive path and allows for innovation. Many builders use the EnerGuide for Houses rating service to meet the performance path requirements.
This path gives step by step instructions for compliance, all of the requirements are laid out.
For the building envelope, that includes the following major areas:
Protection and continuity of insulation
Spaces heated to different temperatures
Above Ground Components
Below Ground Components
Continuity and effectiveness of air barrier
Compliance on the trade-off path is broken into two approaches: simple and detailed.
Simple: This permits minor trade-offs of building envelope components to allow for the reduction in the thermal performance of one assembly, while compensating with increased performance of an assembly in another component. Trade-offs have limits on reductions, and windows cannot e traded off for walls, or visa versa. Trade-offs are permitted between:
above grade walls, floors and roofs
between windows that are located on the same wall
Detailed: Requires energy modelling, can only trade within each section (building envelope only)
Another trade-off path, but can trade off higher/lower performances across sections
Requires energy modelling
Use a nationally recognized energy modelling program like EnerGuide for Houses
Performance-Based New House Programs
R-2000: This program is available only in Canada. Recently updated, the standard requires builders to have 3rd party verification of the thermal enclosure, the heating and cooling systems, whole-house ventilation and water conservation measures. An R-2000 house uses about 50% less energy for space and water heating than a code-compliant house.
Energy Star for New Houses: To qualify under this program (in Canada and US) builders are required to have 3rd party verification of the thermal enclosure, the heating and cooling systems, water management and lighting and appliance loads. ENERGY STAR certified houses use 15 to 30 percent less energy than code-compliant new houses.
Built Green Canada: Built Green Canada is an industry-driven certification programs have been created to encourage and facilitate sustainable business practices. The programs address seven key areas of sustainable building: energy & envelope, materials & methods, indoor air quality, ventilation, waste management, water conservation, and building practices.
Net Zero Home Label:This program is run by the Canadian Home Builders’ Association (CHBA). It has a two-tiered technical requirement that recognizes Net Zero and Net Zero Ready Homes. CHBA members must be certified to build or renovate to Net Zero under this program.
Passive House: Is a performance-based program for energy efficient houses from Germany that has been modified for the range of North American climates. A Passive House can use up to 85% less energy for space heating and 45% less energy for cooling than a code-compliant house. The standard is based on comfort and performance criteria for space heating and cooling only. Passive House is based on work that Canadians did in the 1970s. The Saskatchewan Research Council (SRC), with Harold Orr and Rob Dumont, designed and built a superinsulated house that inspired Wolfgang Feist, the founder of the original PassivHaus program.
LEED for Homes: Leadership in Energy and Environmental Design (LEED) is a green building rating system that is available in both Canada and the US. Houses built under this standard must meet or exceed benchmarks for in eight areas: site selection, water efficiency, energy efficiency, materials selection, indoor environmental quality (also called indoor air quality), location and linkages, awareness and education, and innovation. Each category has a number of mandatory measures, and a minimum point amount is required for a house to be certified. The more points, the higher the certification: certified, silver, gold or platinum.
Living Building Challenge: This program is focussed mainly on projects at the institutional/commercial scale, not single homes, although there are some certified homes in the program. It is likely the most rigorous formal program out there for quantifying and qualifying sustainability in the built environment. The Challenge has seven performance categories: Place, Water, Energy, Health & Happiness, Materials, Equity and Beauty. Projects are rated on the number of points they get in each performance category.
When it Goes Wrong
The biggest enemy of any building is moisture, regardless of climate. Buildings can be damaged by rain or snowmelt, by high humidity levels, by condensation. Moisture affects the performance, safety, and durability of buildings. This is why an understanding of building science is so important.
A new building design, or a retrofit plan both need to be informed through building science to avoid moisture-related problems caused by:
Poorly placed vapour barriers that allow water vapour to move into assemblies without drying capacity
Dew points that cause moisture to condense out into wall cavities
Masonry-faced wall assemblies that are prone to solar vapour drive
Flashing details that cause capillary action leakage around openings
Poor insulation and air sealing in the attic that causes ice damming
Non-continuous drainage planes
Aesthetic design considerations that work in one climate zone don’t necessarily work in another.
The actual design of a building can cause problems, but so can poor construction practices. There’s an overlap between design and construction - the builder constructs what the designer has specified. However, poor construction practices can wreak havoc with control layers. Poorly installed batt insulation can reduce the thermal performance of a wall system significantly, a damaged air barrier increases air flow through assemblies, resulting in higher heat loss and possible moisture problems. Moisture issues are often the number one source of callbacks, requests for quotes and homeowner concern.
While performance problems stem from the building design and specification, poor construction practices are also a factor in defects and failures. Construction problems are caused by people and processes, and are often the result of inefficient systems of management. Builders and renovators rely on processes, procedures, and practices from the start of the bidding process, to handing the key over to the client once the project is finished. When one or more of the three Ps (process, procedures, and practices) are ignored, or don’t exist, that’s where problems occur in the management of any project. These can be classed as system problems, and they are common in construction and renovation projects, because there are so many moving parts. System problems are where builders and contractors lose money to inefficiencies in the process, and to callbacks due to avoidable defects. The project management team is responsible for solving everything from inaccurate project assessments and incomplete bidding, to hiring practices and solving turnover problems, to scheduling problems and budgeting.
In many jurisdictions, new builders are required to work under new home warranty programs. These programs lay out the minimum acceptable performance or condition for new homes that homeowners should expect, and that builders must meet. Guidelines in these programs set out measurable benchmarks for frequent and typical items that deal with quality of work and material defects. Exceeding the guidelines (which, like the building code, are the minimum requirement) improves customer service and reduces callbacks. Renovators and other contractors who are not required to work under new home warranty programs can take a cue from these types of guidelines to help improve their customer service and reduce callbacks.
As an example, here is an overview of the Construction Performance Guidelines from Tarion, Ontario’s New Home Warranty Program:
Essentially, the warranty program requires builders to provide new homes that are free from such potentially damaging problems as:
One Year Warranty
Deposit protection and delayed closing compensation
Defects in workmanship and material
Building Code violations
Two Year Warranty
Water penetration through the basement or foundation walls
Water penetration into the building envelope
Electrical, plumbing and heating delivery and distribution systems
Defects in exterior cladding
Building Code that affect health and safety
7 Year Warranty
Major Structural Defects
Two case studies in poor design and construction
Two high profile examples of problems with poor design and construction are the Leaky Condos in Vancouver, and the ‘Make it Right’ houses in New Orleans. Both of these examples show what happens when aesthetics, style, and details that don’t consider the power of water are designed into the fabric of buildings.
Conventional v. High Performance Building Envelopes
With conventional construction in cold climates, codes have developed prescriptive ways to counteract air, moisture and heat flows. For example, a typical wall system in Canadian housing is wood-framed with fibrous insulation in the cavities, a vapour barrier to the warm side of the insulation (that also acts as an air barrier when sealed), and sheathing under cladding on the cold side of the insulation. There are many weak points in this assembly that can decrease the lifespan of the wall and affect the comfort and health of the occupants over time. Thermal bridging through framing decreases the overall performance of the building. The uninsulated, cold surface of the sheathing that faces the wall cavity is also a problem, as it can be where water vapour condenses. If the wall assembly has an ineffective vapour barrier, and moisture travels into the wall and the drying potential to the exterior is minimal, then the wall will experience moisture damage. This is the basis for the mantra of ‘vapour barrier on the warm side of the insulation’. We want to stop, or minimize, water vapour from entering the wall cavity so it won’t condense out and cause structural problems.
High performance housing can actually bypass this issue. One common approach to high performance housing includes wrapping the walls with an exterior insulation layer. This effectively stops thermal bridging, improving the performance of batt insulation behind it. When the exterior insulation is adequately thick, it also keeps that interior face of the sheathing warm, so water vapour does not condense out. It doesn’t, by itself, stop water vapour from moving into the wall, so there still needs to be a vapour barrier or retarder and an air barrier. The wall still needs a way to dry, either to the inside or to the outside.
Houses are expensive to build and maintain. As energy consumption targets get lower, the expense of operating the house goes down, but there is a capital cost associated with getting to those targets.
Flexible design takes into account the fact that, over the lifespan of the house, there will be several iterations of ‘household’ and ‘occupants’. Anticipating change in use and pre-planning for renovations or retrofits that could suit various occupancy levels is the key to flexible design. Some examples of flexible design features include:
Rooms that can be revamped to create in-law suites
Dens that can be turned into guest rooms
Dining rooms that can used as offices or playrooms for young families
A house that can accommodate a family, but can be split into two small suites in the future
A house that is built out for a small household, with unfinished spaces allowing for household growth
Some design aspects that allow for flexible space use:
Clear span floor joists (no load bearing walls to move)
Interior wall framing that has door openings built in
Unfinished attic, insulated in sealing, prewired/preplumbed
Installing fireproofing/soundproofing between floors to allow separate suites
People’s ability levels change. Typical house design and construction is based on able-bodied occupants with the mobility to walk up and down stairs, to stand and work at a kitchen counter, to turn around in a small bathroom. There is no assurance that any one of us will be able bodied for our whole lives, and there’s a high probability that we will not be able bodied our whole lives.
Twenty percent of the population has a mobility problem. Renovating existing buildings and designing new ones to accommodate various levels of mobility, motility, and a wide range of disabilities (physical and mental) is an important part of creating sustainable housing and community.
There are at least four recognized approaches to design and plan for the current and/or future needs of occupants:
Accessible: this is the lowest bar - in public buildings, it means that a wheelchair user can get into the premises without help, and once in, has access to a bathroom.
Barrier Free: this refers to a floor plan that is designed to allow a wheelchair user to use at least the main floor without special accommodations or equipment required to access the main floor of a house. A multi-story house can be considered barrier-free as long as there is an accessible bathroom and bedroom on the main floor.
Aging in Place: this refers to new construction or renovation plans that allow a person to live in their own home and community safely independently and comfortably, regardless of age, income or ability level (definition is from US Centers for Disease Control and Prevention). This approach only addresses accessibility challenges that have been planned for as occupants age. More on aging in place here.
Universal Design: this approach starts from the expectation that a building must be designed to be accessed, understood, and used to the greatest extent possible by all people regardless of age, size, ability, or disability. In other words, a building should be designed to meet the needs of all the people who wish to use it. More on universal design here.
Not only could there be changes or alterations in how the house is used, there could also be anticipated changes in how the house could be heated or cooled, or how energy could be supplied. Preplanning for on-site renewables is another layer of anticipating change in how the house is used. In its first iteration, it’s an energy consumer, but a small amount of preplanning when building or renovating can mean that the second iteration makes it an energy producer.
Preplanning for renewable energy allows for a wider range of options for future homeowners. Natural Resources Canada provides a document that details all aspects of preplanning for both PV (solar electric) and for solar thermal (hot water) systems on detached and attached houses. Design considerations for both PV and solar thermal pre-planning include:
Mechanical Room Floor and Wall Space
Following is a summary of the overall requirements for solar thermal or PV pre-planning. Conduit is used in place of wiring or plumbing to allow for the widest range of system options for future homeowners. A link to the pdf of the full Solar Ready Guidelines manual is provided below. Note: check the NRCan website for most current version of the manual.
Minimum 12 ft x 10 ft (3.7 m x 3 m) unobstructed area
Orientation of roof is east to west, with azimuth angle of 90° to 270° from true north
Roof area does not extend past exterior load bearing wall line (avoid overhang areas)
Recommended roof pitch 5/12 to 18/12
1” (2.5cm) nominal diameter conduit of rigid or flexible metal, rigid PVC, liquid tight flexible conduit or electrical metallic tubing
Continuous from accessible attic/roof location to mechanical room wall space (bends/elbows acceptable)
Solar Thermal Conduits
2 * 3” (7.6cm) nominal diameter conduits or 1 4” (10.2 cm) nominal diameter conduit
Straight and continuous run from accessible attic/roof location to mechanical room
Installed entirely within building envelope
Two ‘tee’ connections on the existing water heaters cold inlet
A ball valve between ‘tees’, left in open position
Small length of pipe extending from both ‘tees’ fitted with ball valves and caps.
One 110V standard outlet installed within 72” (189 cm) of future position of solar thermal storage tank in mechanical room
Floor space for future solar thermal storage tank 36” by 36” (91.4 cm x 91.4 cm) with clearance height of 72” (183 cm)
Future storage tank location should be close to existing hot water tank, leaving access to doors, hallways, other appliances and equipment
Wall space of 36” by 36” (91.4 cm x 91.4 cm) is adequate for either solar thermal controls or PV controls, double the area if installing both
Natural Resources Canada Solar Ready Guidelines.
As well as these solar ready guidelines, roof loading may need to be addressed. The Truss Plate Institute of Canada (TPIC) published a technical bulletin for new construction taking into consideration the extra loading that can be expected when solar panels are installed. The bulletin is specifically for truss design in compliance Part 9 of the National Building Code of Canada.
Resiliency and future proofing look ahead to possible weather extremes due to climate change. High performance housing can improve how a house performs in weather extremes in several ways by providing fail-proof, multiple control layers that provide:
Continuous drainage plane
Proper water management
High thermal envelope
Reducing the overall energy load through improving the building envelope leads to a house that can hold comfortable ambient indoor temperatures for a longer time, keeping occupants safe during power outages.
There are three key things to keep in mind for resilient future-proofing:
Keep it simple
Passive systems are better than active
Moving parts fail
Durable exterior materials for cladding and roofing that are fire resistant in areas where wildfires are a known hazard. Include ‘firewise’ landscaping designs, drought tolerant plantings.
New construction should be built out of flood and wind zones, take advantage of passive solar where possible.
Consider hurricane/strong wind design, ensure the house has continuous connection from the foundation to the roof. Metal strapping and hangers improve resistance to wind as well as seismic loading.
Simplify new construction house shape, orient the roofline to reduce wind pressure.
Plan for, or install, a rainwater harvesting system to ensure a supply if water service is interrupted. Greywater (water from showers and sinks) can be recycled into landscaping or flush toilets in some jurisdictions.
Redundant power systems. A back-up power source (generator) can be hardwired to a subpanel that bypasses all other circuits except for crucial loads like well pumps, ventilation equipment, heat pump, fridge/freezer, some lights, and a few outlets.
Here is an excellent article from EcoHome that details future proofing in a cold climate.
While smart home controls are part of future proofing, future proofing is not just about wires. In fact, with the rapid changes that are happening across the Internet of Things, it can make sense to future proof smart home controls and control costs by not installing wires. One approach to future proofing for smart home controls is to provide electrical conduit to all outlets and switches. Ensure the conduit is large enough to run several cables, thick cables, and HDMI/USB/other connectors on pre-made cables. Like improving the building envelope, the most cost effective plan is to think ahead and avoid as much demolition or re-work as possible. And, like improving the building envelope, simpler geometry and planning at initial construction or retrofit can help make this aspect of future proofing successful versus digging up, drilling into, knocking down, routing around house and landscaping features. Run a length of string through the conduit, cap each end and mark where the ends are in the house plan.
Wireless options are available, of course, but keep in mind that wifi capacity is not limitless, batteries go flat, radio is subject to interference. Also, wireless transmitters need power cables. Industry recommendations are to use wires where possible and to keep wireless for ‘special’ things.
The above summary of smart home wiring of an excellent resource for all things smart home by an installer, not a provider.