This is the third in a set of articles that walks you through how to optimize the equipment and systems that homeowners use day-to-day, like hot water, lighting, and appliances.
The first articles in this series on Occupant loads deals with domestic hot water, also known as DHW, equipment. The second article discusses how to reduce DHW loads at the design phase of a new build or renovation project. This third article discusses Occupant Loads in general, and how energy efficiency can be improved at the end use (where the occupant has control).
Here’s the evaluation form, so you can rate yourself on your existing understanding of what builders and contractors can do to reduce occupant loads. 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!
If you find Occupant Loads a challenge, read on. There are links to other resources in this article.
If you’ve got this part of the competency down, tune in next week for the fourth part of High Performance Housing, Renewable Energy Systems.
The one thing that cannot be accurately predicted or controlled in a high-performance house or energy retrofit is occupant behaviour. Occupant behaviour is driven by many factors, and dictates how much energy is used on 'baseloads' - the end-uses of energy that cannot be controlled by the builder or renovator.
Studies have shown wide variation in household energy use, energy use in the residential sector accounts for more than 20 percent of all energy use.
As the house moves to high-performance targets like Net Zero or Passive House, controlling the occupant loads rises in importance. While any heat produced by occupants or their activities becomes part of the heating regime of a high-performance house, reducing energy is the key in this area, to minimize the impact of lighting, electronics and appliances on the sizing of an on-site energy generation system.
When whole-house energy targets look at energy intensity (the amount of energy used per person, or per square foot, on an annual basis) one of the major contributions to high energy intensity rates is the way that occupants deal with energy. The impact that occupants have in the energy performance of a building can be significant.
The results of home evaluations and assessment that provide modelling to predict energy use are typically skewed from the actual energy use due to the way that occupants behave. Energy use varies from one household to another, appearing irrational or unexpected in terms of energy conservation, yet making complete sense in the context of family schedules, occupancy patterns, and comfort preferences.
Occupant behaviour is influenced by quantifiable and hard-to-measure factors, as well as external features, such as politics, economics, and culture. Some objective, physical, and measurable aspects include: climate, air velocity, temperature, noise, building controls, occupancy levels (how long are people in the house over the course of a day), and activity type. Other factors that are more challenging to measure are subjective, for example, individual perception of comfort, expectations of what comfort should be, gender, age, health considerations, and social interaction.
One of the key challenges for a builder or renovator working on high performance projects is this: As the performance of the house improves, the space conditioning load (heating and cooling) is reduced, and the impact of energy loads that are driven by occupant behaviour increases. As you improve the building envelope and drop the space heating and cooling loads, the overall amount of energy is reduced, but this also changes the proportions of energy end uses. For example, conventional housing energy use can be split out like this:
65% space conditioning
17% water heating
As the house envelope moves towards net zero energy, or net zero energy-ready, the energy loads drops, but the split on energy use looks like this:
26% space conditioning
20% water heating
So, managing the lighting and appliances, as well as overall electricity use and water consumption becomes a bigger challenge. In addition to dropping energy loads, these end-use conservation measures help to reduce greenhouse gas emissions associated with electricity production.
Lighting, electronics, and appliance energy use is often referred to as ‘base load.’ This term is not quite accurate. Load is the amount of power in the electrical grid. Base load is the level that it typically does not go below, that is, the basic amount of electricity that is always required. Peak load is the daily fluctuation of electricity use. It is usually lowest in the wee hours of the morning and highest in the early evening. When referring to a house, the base load is the amount of energy that the house requires when there there is no heating or cooling load. Occupant load is a better term.
Reducing Electrical Loads
The first thing to look at when reducing lighting loads in new construction or major renovation is the lighting plan. Proper lighting design can lead to fewer bulbs at lower wattage and the right lumen levels for the type of lighting needed. Lumens indicate the amount of light being generated. (Wattage is a measure of energy use, not light strength.)
Kitchen and bathrooms typically need ambient lighting and high-lumen, directed task lighting, while other rooms might only need ambient lighting with lower levels of lumens.
Pot lights, also called can lights or recessed lights, cause a significant amount of air leakage when installed in ceilings that back onto attic spaces. They can also be the source of heat loss via air flow into floor joist cavities, especially in existing houses where stopping air flow between floors is nearly impossible. While it is best to avoid potlights, use airtight units if you can’t avoid installing units in areas where they add to heat loss.
To optimize a lighting plan, choose energy efficient bulbs.
The EU began a phased ban of incandescents in 2009. Canada followed suit banning the manufacture and import of higher wattage incandescent bulbs beginning in 2014. According to the US Department of energy, rapid adoption of LED bulbs would collectively save $265 billion over the next 20 years - eliminating the need to build 40 new power plants and save hundreds of millions of tons of greenhouse gases from entering the atmosphere.
Compact Fluorescent Lights (CFL)
CFLs are miniature versions of full-sized fluorescents. They screw into standard lamp sockets. CFLs can be used in recessed fixtures, table lamps, track lighting, ceiling fixtures and porch lights. Three-way and dimmable CFLs are also available.
CFLs use 50 – 80% less energy, and last up to 10 times longer, than incandescents. A 22 watt CFL has about the same light output as a 100 watt incandescent. A single 18 watt CFL used in place of a 75 watt incandescent will save about 570 kWh over its lifetime. Replacing a single incandescent bulb with a CFL will keep a half-ton of CO2 out of the atmosphere over the life of the bulb. Saving electricity reduces CO2 emissions, sulfur oxide and high-level nuclear waste.
CFLs give a warm light, and electronic ballasts don’t flicker or hum. CFL bulbs are rated with a Kelvin or ‘K’ number that indicates what type of light it gives. CFLs with K numbers between 2700-3000 are similar to incandescents. As you go up the K number scale the light gets bluish and closer to daylight.
CFLs are an excellent source of energy-efficient lighting, but they have some limitations:
Their rated lifetimes of 10,000 hours are reduced with frequent on/off cycling. Closets and other places where lights are needed for brief illumination should use LED bulbs.
Not all CFLs can be used on dimmer switches. Using a regular CFL with a dimmer can shorten the bulb life span.
Outdoor CFLs should be covered or shaded from the elements.
Low temperatures may reduce light levels – check the package label to see if the bulb is suited for outdoor use.
CFLs contain small amounts of mercury, which is a toxic metal that can be released if the bulb is broken or during disposal.
Light Emitting Diode (LED)
LEDs are small, very efficient solid bulbs, which makes them far more durable than traditional bulbs of any type. When first developed, LEDs were limited to single-bulb use in instrument panels and electronics. A significant feature of LEDs is that the light is directional. Incandescent bulbs spread the light more spherically. This is an advantage with recessed lighting or under-cabinet lighting, but it is a disadvantage for table lamps. New LED bulb designs address this directional limitation by using diffuser lenses and reflectors to disperse the light more like an incandescent bulb. LED technology is advancing rapidly, with many new bulb styles available, including ones with standard bases that fit common light fixtures. Two common types of bulbs are:
Diffused or Omnidirectional Bulbs. Clusters of LEDs are covered by a dimpled lens which spreads the light out over a wider area. Dimmable Globe LED Bulbs. These 10 Watt bulbs produce light equivalent to a 40-watt incandescent bulb. They are dimmable from 100% to 10%, with a 200 degree beam angle to cast light in a wide area.
LEDs are more efficient than other types of bulbs, using only one third to one thirtieth of the energy of incandescents and CLFS. Typical LEDs for household fixtures use between 2 and 17 Watts per hour of service. LEDs reduce energy consumption in a second way: a fixture will produce 3.4 BTU/hr during operation, compared to about 85 BTU/hr for an incandescent bulb. This cool operating mode means lighting does not add to cooling loads.
In addition, LEDs can last up to ten times longer than CFLs, and 40 times longer than incandescent bulbs.
Link to Light Bulb Comparison Charts.
Install motion sensors in medium or low-traffic areas, where occupants could accidentally leave a light on and not notice. The list of areas where motion sensors make sense includes closets, bathrooms, entrances, utility closets, garages or guest rooms. A motion sensor makes more sense when there are multiple light fixtures with multiple bulbs on one switch.
Motion sensors have a small phantom load, about one Watt of energy on standby mode (typically 23 hours a day) and 5 Watts in active mode (for an hour a day). This translates into about 0.84 kilowatt hours a month, more than 10 kilowatt hours a year. That cost is equivalent to the energy cost of leaving a single 60 watt light bulb on for 167 hours in a year.
Many sources note that installing efficient lighting is a smarter choice when it comes to energy savings, as the cost of a single switch outweighs the savings from LED or CFL bulbs. While the cost of a single motion sensor may outweigh the probable energy savings, there are two main non-energy benefits to motion sensors:1.Convenience
A motion sensor at the front door, means occupants have light when they or guests arrive, not all evening or all night.
For occupants with disabilities, motion sensors mean they don’t have to reach for a wall or lamp to light a room.
Aging in Place: occupants don’t have to worry about checking if any lights are left on.
In the case of a home break in, motion sensor lights may deter criminals who would have otherwise gone unnoticed.
It’s an effective way to improve home security without spending a lot of money on a security system
ENERGY STAR is the symbol for energy efficiency. It’s a label created by the U.S. Environmental Protection Agency and the U.S. Department of Energy to help consumers save money and minimize air pollution. It is used in both Canada and the US to indicate those consumer items that meet or exceed a certain threshold for energy use when compared to other models that have the same features.
The ENERGY STAR logo is found on clothes washers and dryers, refrigerators, dishwashers and room air conditioners that are significantly more energy efficient than the minimum government standards, as determined by standard testing procedures. The amount by which an appliance must exceed the minimum standards is different for each product rated, and depends on available technology. Typically ENERGY STAR rated units are in the top third of their class.
More information about the ENERGY STAR program is available at
How to use energy efficient appliances for best performance, a resource for your clients
Many devices (e.g., computers, TVs, chargers) draw some electricity even if they are turned off but are in ‘standby mode’. Any appliance or device that has a red or blue (typically) LED light constantly running is in ‘standby mode’. Any device that has a clock in it has a constant electrical draw. In all cases, this electrical draw is referred to as a ‘vampire’ or ‘phantom’ load. Even if these devices are only drawing a small amount of electricity, when added together with other devices around the house, it adds up to wasted energy and money.
Nearly all modern appliances consume power even when they're off. Phantom loads maintain your television settings and allow the unit to power up quickly when you press the "on" button. They keep the clocks going on your DVR player, stove, and microwave.
Phantom loads also keep your wireless network running even when you're not online, and they make sure your wireless printer is ready to print whenever you are. So while appliances have improved in operational energy consumption since the 1990s, that has been offset by an increase of phantom loads. In fact, an international study led by several environmental agencies around the globe put that price at a full 10% of a household’s monthly energy bill.
Depending on the household mix of electronics and appliances with electronics in it, the total phantom load can be upwards of 300 Watts, every hour, every day. That’s over 7 kW a day, nearly 220 kW per month, and almost 2600 kW annually.
Think of electricity as water. You wouldn’t let a faucet run or drip if no one was using it. Energy is a valuable commodity and should be conserved just like water. When you conserve energy, you are also preventing more greenhouse gas emissions.
As a builder or renovator, you cannot alter or control occupant behaviour and consumer choices. Mainly, your role is to inform homeowners.
Here’s a great infographic from Hydro One.
Building in options for homeowners to control their phantom loads is limited to installing ENERGY STAR qualified appliances that have built-in power savings, and ensuring that there are switched outlets in every house. You can provide “smart” powerstrips. These powerstrips have outlets that always have power and other outlets that will automatically cut power to the outlet when the electrical device goes in standby mode or is turned off.
Reducing Total Water Consumption
Water costs money. Town or city dwellers pay water fees to municipal utilities and agencies. Homeowners on unserviced lots, with a well and septic system, pay for the electricity used by the well pump, and in some cases, by an ejector pump to the septic field. Wells and septic systems also have wear and tear in operation, which leads to maintenance, repair, and replacement costs over the lifetime of the services.
Reducing total water consumption takes another step past reducing energy loads for hot water use. In addition to saving money on your client’s utility bill, water conservation helps prevent water pollution in local watersheds. Reduced water consumption also means groundwater sources are preserved. In addition, conserving water saves energy and prevents greenhouse gas emissions associated with treating and distributing water in municipal systems.
Conserving water can also extend the life of septic systems by reducing soil saturation and reducing pollution due to leaks. Overloading municipal sewer systems can also cause untreated sewage to flow to lakes and rivers. The smaller the amount of water flowing through these systems, the lower the likelihood of pollution. In some communities, costly sewage system expansion has been avoided by community-wide household water conservation.
The challenge for the builder or renovator is there is no way to control the occupant behaviour, so we have to install equipment and fixtures that will help to minimize water use, but not restrict it.
Water-saving measures can reduce in-home water use by 35%. The average household, using 1325 L (350 gallons) per day, could save 475L (125 gallons) of water per day. That’s a reduction of 166,560 litres (44,000 gallons) in water use per year.
Installing low-flow fixtures is a place where we can reduce the overall water consumption as well as the DHW load in ways that don’t negatively impact occupant behaviour, or limit the amount of hot water available to the occupants. Water reduction starts in the bathroom, as 75% of water used indoors is in the bathroom, 25% of this is for the toilet.
Replacing an old toilet with an ultra-low volume (ULV) 1.6 gallon flush model represents a 70% savings in water and will cut indoor water use by about 30%.
Low-flow toilets were introduced in the early 1980s to replace 3 to 5 gallon (12 to 18 litre) flush volumes with 1.6 gallon (6 litre) flush volumes, in single and dual flush models. The first generation of these units had performance problems: fouling or blockages in the trap or supply line and blockages in the drain pipes.
Revised designs dealt with the problem by increasing the diameter of the opening between the tank and the bowl and widening the trap at the bottom of the bowl. The industry has also introduced high-performance 4.5-litre and 4.8-litre models equipped with a simplified mechanism, an excellent compromise between six-litre models (which use more water) and mechanically complex double-flush models.
Since 2003, more than two-thirds of the toilet models on the market have been evaluated by an independent body that measures the quantity of solid waste they can evacuate with a single flush. Their performance is published in the report of the Maximum Performance Testing of Popular Toilet Models (MaP) program.
The U.S. Environmental Protection Agency’s WaterSense program, guarantees that the toilet will evacuate at least 350 grams of waste per flush. Given that an average of 150 grams of waste has to be flushed with each use, any toilet providing this capacity should be quite adequate for most people’s needs.
Installing a low-flush toilet could be a mistake in a basement with old drain pipes. The smaller volume of water, combined with a lack of height and low angles in sewers, may lead to blockage if sediments or rust have accumulated in the pipes or if the backup valve is worn out.
Quality of the porcelain: The quality and thickness of the glazing applied to the toilet are what will give you ease of maintenance and a long-lasting look. The length of the guarantee on the finish and the manufacturer’s reputation are the best indicators of quality.
Insulation inside the tank: This is essential to prevent occasional wetness caused by condensation (when the water is very cold but the surrounding air is warm and humid).
Traps: The distance between the wall and the middle of the trap is an important consideration both when conducting the renovation work and when buying the toilet. The standard distance is 12 inches, but some toilets are designed for distances of 10 or 14 inches. At least one American manufacturer offers a toilet with a plastic trap of 10, 12 or 14 inches.
Round or elongated bowls: Models with elongated bowls are preferable for comfort but are not always suited for tight spaces.
Height of the bowl: To help elderly people get up easily from the toilet, there may be a temptation to install a raised bowl. However, for most people, this raised position is quite different from the most natural bodily position for using the toilet. Installing a well-adjusted grab bar will often be more useful than a high bowl, though a high bowl may be appropriate for someone with reduced mobility or who is very tall.
An easy water conservation measure for renovations is to switch out old showerheads with inexpensive water-saving low-flow showerheads. This change out can help the homeowner achieve immediate water savings of 25%–60% from shower use.
Most jurisdictions in North America require new showerheads and faucets to have low flow rates for new construction. Flow is the volume of water delivered, measured in litres or gallons delivered per minute (l/min or gpm). Water pressure affects the rate of flow. Higher pressure results in a greater volume of water. Showerhead performanc is typically rated at at 80 pounds per inch (psi) (that’s 551.6 kiloPascals for those who think in metric)
Showerheads and faucets that pre-date 1992 deliver 19 to 30 l/min (5 to 8 gpm) of water at 80 psi. The current standard for low flow heads is 9.6 l/min (2.5 gpm) at 80 psi. Some low flow shower heads deliver only 6 l/min (1.6 gpm).
Here’s the math:
The average shower lasts 5 to 10 minutes. A water saving showerhead, uses about 7 l/min (1.8 gpm) of hot water, assuming that some cold water is mixed in. So, assuming an 8 minute shower, consumption is about 56 litres (14.5 gallons) of hot water per shower or 224 litres (58 gallons) a day for a family of four. Compare to an older model that uses about 19 l/min (5 gpm): 152 litres (40 gallons) of hot water per shower, or 608 litres (160 gallons) a day for a family of four.
Look for units with a WaterSense label, which mandates using 2 gpm or less. WaterSense is a US government program that certifies water-saving devices like showerheads and faucets, much like Energy Star recognizes energy efficient appliances and some electronics.
Showers and faucets together account for about 23 percent of the water consumption in a house, more than toilets or clothes washing.
Low-flow faucets designed to federal standards (2.5 gpm at 80 psi) use sensors as well as aerators to reduce water consumption. There are several low-flow faucet technologies for kitchens and baths, including a metered-valve faucet that delivers 0.25-gallon of water and then automatically shuts off. Self-closing faucets are spring-loaded to shut off the faucet a few seconds after the user turns it on. Ultrasonic, or infrared-sensor, faucets automatically activate the water flow when hands are detected beneath it and automatically shut it off when the hands are removed. Foot controls allow you to activate a faucet at a set temperature by tapping your foot on a pedal. Finally, a conventional faucet can be retrofitted simply and inexpensively by replacing the screw-in tip of the faucet with an aerator.
In the kitchen, besides the faucet, in-sink ‘garburators’ require lots of water to operate properly, and also add considerably to the volume of solids in a septic tank, which can lead to maintenance problems.
When specifying, installing or replacing appliances like clothes washers and dishwashers, choose ENERGY STAR® rated units to ensure the occupants will reap the benefit of lower DHW loads. For example, an ENERGY STAR-qualified dishwasher can uses 31% less energy and 33% less water than a comparable conventional unit.
The most efficient clothes washing machines use as little as seven gallons per load, compared to 54 for a traditional washer. A high efficiency (HE) washer should easily pay for itself over its lifetime in water and energy savings. New Energy Star rated washers use 35 – 50% less water and 50% less energy per load.
Here is a good article about water-saving frontload washers.
When you install or replace a dishwasher, specify an ENERGY STAR certified dishwasher. These units use, on average, 12% less energy and 30% less water, than a standard model. Other specifications that will help the occupants in their water conservations efforts:
Choose a dishwasher with an “energy-save” or “light wash” cycle which uses less water and operates for a shorter amount of time.
Choose a dishwasher with an “air-dry” option which uses circulation fans. This uses less power than “heat-dry” modes.
Look for a dishwasher with a hot water booster or internal water heater that raises water temperature inside the dishwasher.
“Grey water” is the water draining from sinks, bathtubs, and clothes washer, which can be used to water plants (as opposed to “black water” from toilets, which needs to be treated).
In some jurisdictions, codes allow for the installation of a grey water system, which reroutes water from the drains to your landscape. European jurisdictions have been leading the way in adopting this type of technology. The simplest systems harvest only water from the washing machine, which can add up to thousands of gallons per year.
Outside the house
If your reno or new build project encompasses landscaping, use drought-resistant grasses. Many beautiful native shrubs and plants thrive with far less watering than other species. Native plants will use less water and be more resistant to local plant diseases. Consider applying the principles of xeriscaping for a low-maintenance, drought resistant yard. Plant slopes with plants that will retain water and help reduce runoff, and group plants according to their watering needs. In borders and around trees, mulch will slow evaporation of moisture while discouraging weed growth. Adding 2 – 4 inches of organic material such as compost or bark mulch will increase the ability of the soil to retain moisture. Use rain barrels or a catchment system to capture rainwater from the roof. Plants prefer untreated water, so your client’s garden will be healthier.
WaterSense is a U.S. Environmental Protection Agency (EPA) program designed to encourage water efficiency in the United States through the use of a special label on consumer products. Created by the US Environmental Protection Agency (EPA) in 2006, WaterSense makes it easy to find water-efficient products that have undergone independent certification that verifies and tests products for: conformance to WaterSense specifications, efficiency, performance, label use and more
LInk to an article showing water consumption breakdown.
And article from whole building design on water conservation measures.
Direct link to the US EPA’s Watersense program website.
Link to Environment Canada’s webpage on water use.