Learn From The Industry Experts!
air sealing priority guide
the first 5 places to air seal in any house:
what to fix before you insulate, renovate, or upgrade your HVAC
Most houses leak air in the same places.
Those leaks make rooms feel cold, create drafts, contribute to moisture problems, increase heating costs, and can make insulation, heat pumps, and ventilation systems perform worse than expected.
The good news?
You don't have to tear your house apart to start improving comfort.
The Air Sealing Priority Guide shows you the first five places to look, what to fix, and why these areas matter more than almost anything else you can do to improve the performance of your home with the smallests budget possible.
✔ understand where houses actually leak
✔ learn what to fix first
✔ avoid expensive renovation mistakes
✔ improve comfort and reduce drafts
✔ understand the connection between
air leakage, moisture, and ventilation
why is my house drafty?
If you've found this page because you're wondering:
Why is my house drafty?
Why is one room colder than the rest?
Why does my house feel cold even when the heat is running?
Why do my windows sweat in winter?
Why is my attic moldy?
Why did I add insulation and still feel uncomfortable?
You're not alone. In most homes, these symptoms have the same root cause: uncontrolled air leakage.
Air is constantly moving through cracks, gaps, holes, and joints in the building envelope. When air moves, moisture moves with it. And that movement affects comfort, energy efficiency, indoor air quality, and durability, and can be the cause of condensation and mold problems
Many homeowners spend thousands of dollars on insulation, windows, and HVAC upgrades before addressing the underlying air leakage problem. The result?
Disappointment and frustration.
symptoms
root causes
Drafts
Cold Floors
Condensation
Musty Smells
Uneven Temperatures
Attic Leaks
Stack Effect
Rim Joist Leakage
Service Penetrations
Foundation transitions
most houses leak in the same places
why some houses never feel comfortable
One of the biggest myths in home improvement is that every house is different. While every house is unique, the vast majority of air leakage occurse in a handful of predictable places, based on physics. These areas are responsible for a large amount of heat loss, comfort problems and moisture movement.
The Air Sealing Priority Guide focusses on the five leakage zones that deliver the biggest return on effort. Fixing these areas first can dramatically improve comfort and reduce unnecessary energy loss.
what's inside the guide
zone 1
Attic Hatches & Sealing Penetrations
zone 2
Top Plates & Attic Bypasses
zone 3
Rim Joists/Headers
zone 4
Foundation-to-Wall Transitions
zone 5
Mechanical Penetrations
Warm air naturally rises. The top of the house is often the biggest source of uncontrolled air leakage. While hidden pathways inside walls and ceiling assemblies can act like chimneys, allowing warm air to escape into attics. Learn how to identify and address:
- Attic Hatches
- Pot Lights
- Fan Housings
- Plumbing Penetrations
- Wiring Penetrations
- Bypasses at top plates
While air rises and leaves the house at the top, air leakage often starts at the bottom of the house, because the foundation area plays a major role in driving the stack effect. Air leakage often starts at the bottom of the house, and it's often one of the most overlooked leakage location in many homes In fact, it can be the single large air leakage source in a house. Learn why rim joists matter and how they contribute to cold floors and comfort complaints.
Every hole cut for pipes, ducts, vents and mechanical systems creates opportunties for uncontrolled air flow. Learn what to look for and where problems commonly occur.
air sealing before insulation?
yes.
One of the most common renovation mistakes is adding insulation before addressing air leakage.
Insulation slows heat flow,
Air sealing controls air movement.
Those are not the same thing.
Air can move through many insulation materials, reducing their real-world effectiveness. That's why building science professionals often focus on controlling air movement before adding more insulation.
The guide explains where air sealing typically provides the biggest benefits and why sequencing matters.
air leakage, moisture, and mold
It's common to think that mold is an insulation problem.
Often it's an air leakage problem.
Warm indoor air contains moisture. When that air leaks into colder building assemblies, condensation can form. Over time, this can contribute to window condensation, mold growth on the walls, attic mold, material deterioration, and indoor air quality issues.
The guide explains how air leakage and moisture are connected and why understanding that relationship can help prevent expensive mistakes.
why air sealing comes before bigger upgrades
who is this guide for?
Homeowners trying to solve drafts, cold rooms, moisture issues, condensation, comfort problems
Owner-Builders planning new construction or renovations and wanting to avoid expensive mistakes.
Renovators and Contractors looking for practical building science knowledge that improves project outcomes and reduces long-term callbacks.
Anyone planning a retrofit before insulation, heat pumps, windows, ventilation upgrades, or major renovation work.
who's blue house energy?
Blue House Energy is an online building science education company that has trained more than 10,000 construction and renovation professionals since 2012.
Our goal has always been simple: help people understand how buildings actually work so they can make better decisions, avoid costly mistakes, and build healthier, more durable homes. Our mission is: it's not OK to waste energy: yours, or the planet's. We want you to get the biggest improvements possible in your new home construction or retrofit project.
who are we?
We’re the building science nerds who’ve spent years in the trenches trying to figure this stuff out too.
Since 1992, Blue House Energy CEO Shawna Henderson has worked in energy efficiency, R2000, Energy Advisor/ERS work, consulting, project management, construction, renovations, and building science education. That means decades spent walking through houses, solving comfort and moisture problems, working with builders and homeowners, and seeing the same building science mistakes happen again and again (and again…).
Our approach is simple. Help people understand the 'why' behind better buildings so homeowners can make informed decisions about the biggest single investment they're likely to make, and so the people doing the work can give their clients the best possible results.
Once you understand the why behind what’s happening inside a building, everything starts making a lot more sense.
• audio learning for builders, contractors, renovators, and housing professionals • online since 2012 •
• 10,000+ professionals trained • BC Housing recognized provider •
• NRCan-recognized Energy Advisor Exam Prep provider•
faqs
why is my house drafty?
Most draft problems are caused by uncontrolled air leakage through the building envelope. The guide identifies the five most common leakage locations and explains what to look for.
should I air seal before adding insulation?
In many situations, yes. Air sealing and insulation serve different purposes, and controlling air movement is often one of the first prioriti for improving comfort and efficiency.
will air sealing reduce moisture problems?
Air sealing can help reduce moisture movement through building assemblies. However, ventilation and humidity control remain important parts of a healthy home.
is this guide suitable for DIY homeowners?
Yes! This guide is written in plain language and focusses on helping homeowners understand priorities and common leakage areas so they can do the work themselves, or make informed decisions about contractor work plans and estimates.
is this guide relevant across Canada?
Yes. Air leakage locations and how to deal with them are based on building science and physics. The 'why' stays the same, but the best materials to use might differ between a mild/moist climate and a cold/dry one.
fix the biggest leaks first
Before you spend money on insulation, a heat pump, windows, or a major renovation, make sure you're solving the right problems and not baking the wrong ones in.
The Air Sealing Priority Guide helps you identify the five leakage locations that matter the moisture and understand why they affect comfort, moisture, durability, and energy performance.
air sealing priority guide:
the first 5 places to air seal in any house
$27
✔ instant digital access
✔ practical, actionable guidance
✔ designed for real homes
✔ written by building science professionals
Want to understand the 'why' behind comfort, moisture, and building failures? Explore Building Science Radio →.