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Residential Energy Efficiency Blog
Thursday, December 31 2020
Towson - Maryland
If you have a Cape-Cod style home and you are wondering if you can air seal and insulate effectively - the answer is yes, however not without a good plan.
Houses with Cape-Cod style framing stem from being built in the 1940's and 1950's when the cost of heating was dirt cheap and insulation was an afterthought.
If you live in this style home, chances are very good that it has not been properly addressed due to the complexities of the way it was built.
Take a look at this recent Cape-Cod insulation project and what steps were taken to seal and insulate. This one is located in the friendly residential Southland Hills community of about 200 homes in the heart of Towson, Maryland. The homes in the neighborhood were built in the 1940s.
The Comprehensive Energy Audit
Foundation -- Air Sealing / Insulation
Air seal any penetrations at the accessible rim joist in the basement with two-part spray foam (~60 linear ft) which will also insulate the area to R-19.
Attic -- Air Sealing / Insulation
Cut access in three wall locations to gain access to upper floor attic. Reinstall the drywall with removable panel for future access if needed.
Treat three existing attic access areas by adding insulation to each and weatherstripping. (2 wall, 1 ceiling)
Add 5-7” of open cell spray foam to the accessible sloped roof surfaces of the kneewall attic areas (~392 sq ft).
Blow 10” of loose fill cellulose to the flat collar attic using the existing ceiling hatch in the closet (~154 sq ft).
Basement Rim & Band Joist - Every Home Should Get this Treatment by the Way
If you are not sure what the rim and band joist are in your basement and if it is accessible for treatment - you are about to find out!
First, put yourself in the unfinished part of your basement. Usually it is a utility room with HVAC, water heater and maybe washer/dryer.
Identify your foundation wall at the top and you have found your rim and band joist.
Take a look at how the electrical "main" is coming through the rim joist in the basement of this Towson, Maryland home performance home. This is happening in a lot of homes.
Look at the size of that hole. And this is the point - it is a hole going directly to the outside which means this:
Summer: humidity infiltration
Winter: cold air infiltration
Just look at those spider webs. The spiders like to make their traps where air is moving. It is instinctual. So if you see a spider web, air is flowing.
Now get your full frame of reference by watching this short video clip that shows where the electrical main and gas line enter into the rim joist from the outside which appears "invisible", but it is not.
Results - A Look at the Final Project and the Test-Out Numbers
Rim and Band Joist Treatment - Closed Cell Spray Foam
Watch the spray foam team treat a portion of the rim and band joist in this up close and personal clip.
Knee Wall Attic Treatment Before / After
Blower Door Results
Many factors drive the overall reduction in leakage that each home is schedule to achieve during a home performance project through the BGE program. I make this very clear to my customers that for every house I am believe we can get 30% reduction and don't there is a home that I am convinced we can only achieve the minimum required to meet the program standards (10%) - only to exceed that by a lot.
As a result of many audits and challenging situations when I was wrong, the partnership I formed with this customer went a long way. We both agreed that 20% reduction was a good target and that due to other factors that were not reported here, we will do everything we can to nail the work scope and see where it takes us.
Ultimately, this home performance project achieved an 11% reduction in leakage.
Initial Blower Door Test In CFM: 3775 Cubic Feet Per Minute at Negative Pressure -50 Pascals
Final Test Out Number: 3255 Cubic Feet Per Minute at negative pressure -50 Pascals
Written by Eric Gans
I have completed over 1000 comprehensive home energy audits. Believe me, you are not the only one trying to figure out why it always feels drafty - even after replacing windows. You may be surprised by what we usually find with testing and building science principles...
If you spent a good sum of money in the spring to replace old drafty windows and you find yourself this winter season with drafty new windows - you are not the only one!
So don't feel bad or lose hope that you can actually have a cozy home. You just might have to look in a few other places to get to the real problem.
As a former window contractor turned certified home energy auditor I have been on both sides of the coin. Early on I was convincing people (with the right intentions and wrong information) to replace windows to solve draft issues.
Now, I am on the other side getting called out to do an energy audit to check windows because it is cold and the new windows still seem drafty after installation.
It took me years to figure it all out, but when you stop and think about it all for a moment - it really makes a lot of sense. So, with the right fixes and new windows, you can move much closer to complete comfort.
Here are five reasons why your new window replacement investment might leave you asking:
Why are my new windows drafty?
1. The Windows Were Not the Draft Source to Begin With
FACT: Windows Account for Only 10% of Total Air Leakage in a Typical Home
A misconception for most homeowners is that windows are the only location in your home's "shell" that air can get in and out.
But, there are many other places around your house that might be much more connected to the outside than windows.
And, a lot of these gateways are hiding in plain sight!
If your home is stubbornly drafty you need to think about your home in three-dimensional ways.
This does not mean that you wasted money on windows, or that you need special glasses. It just means that you need to shift your hunt for the drafts by starting to look up and down instead of only through the sides.
FACT: Most Window Salesman Talk About U-Factor and Solar Heat Gain Coefficient
Guess what...neither measure for air leakage! Why, you ask? It is not as important as they lead you to believe.
Read on to learn about the stack effect and how getting the basics from this physics phenomenon can help you begin to think in three dimensional ways about drafts.
2. Understanding Stack Effect & How it Can Solve Your Draft Issue
In the book Rich Dad Poor Dad by Robert T. Kiyosaki, he talks about how as school children we are never really taught the vital lessons of personal finance and how to stay out of debt and save for the future.
Similarly, I say everyone should learn about the stack effect when ready to purchase a home.
Understanding how it can play a big part in the drafts that are felt around your home could go a really long way towards better comfort and energy efficiency.
The stack effect can be simply understood by taking one concept we all learn as young children: Hot Air Rises
Here is the part they don't tell you when it comes to your home.
When the warm air rises in your house it escapes through all of the holes in your ceiling right up into the attic - especially if there is no air-barrier in place or if the air-barrier is mis-aligned.
Many of the holes where this is happening you cannot see, but they do exist!
This problem causes a conveyor belt in a sense. When the warm air goes out at the top new cold air gets drawn in down low - from the leaky parts of the basement or an open crawl space.
Stack effect is why recessed lights and rim joists should receive way more attention than windows. A slotted recessed light is no match for the warm air pressure and it drags cold air in down low. As a result - your comfort and money go right into the attic.
Slot filled recessed light with light bulb removed.
Leaky recessed lights may be one example of why you feel drafts despite thinking things were sealed up once the windows were installed.
You are not convinced your basement is leaky? Watch this!
Here are a few other articles that you might find useful if you like this one...
The Real Reasons Your House is Always Cold | 5 Easy Ways to Seal Up Your Home
How Much Insulation Does Your Attic Need in 2021? | How Much Does Attic Insulation Cost?
3. Fireplace Flue & Recessed Lights - Sealing Up "Gateways" to the Outside
If you just put brand new windows in and you still feel drafts, then look around a bit. One easy way to find drafts is to look for the "gateways" to the outside.
For example, one out of every five customers that I do an energy audit for do not have the flue shut on their fireplace chimney which is a huge gateway to the outside.
Recessed lights are also gateways to the attic (outside) and it is a good practice to check the dampers on any exhaust fans you have venting to the outside. A mis-aligned, damaged or non-existent damper can be a real draft maker.
Solutions include covering and sealing can lights at the attic floor, improving exhaust terminations and using chimney "balloons" to seal faulty flue dampers.
Check out these unsealed recessed lights.
Watch the smoke demonstrate the air coming through the fixture
4. Improperly Treated Crawl Space/ Basement
If the construction style of your home is on a crawl space that is open, then you might experience high drafts.
An open crawl space will allow unconditioned air into the the crawl space and unless there is a proper pressure boundary separating the foundation area from the room above, then drafts will surely occur through the floor.
If you have a full basement it is very likely that the rim joist in any finished or unfinished area has not been properly air sealed and this will allow air infiltration in the basement area that will cause drafts through walls and floors into the living space above.
How to Seal Up an Unfinished Basement Rim Joist
5. Improperly Installed Windows
Another possibility for drafty new windows, however the least likely, is that the windows were installed improperly or worse yet, not caulked and sealed.
Even if this is the case, it would still be difficult to make a draft problem worse with new windows even if the windows are incorrectly installed due to pressure dynamics in a house.
It is important to note however, that basement windows and windows on the second floor could be susceptible to leakage if not properly installed and sealed due to higher pressure.
Watch this typical replacement window installation to get more perspective on your building's shell.
Only replacing windows is not likely to change whether air is infiltrating into your home.
Watch how a window should be foam sealed once set in the structural framing.
Drafty Window Solutions: What will actually work?
Get a Comprehensive Home Energy Audit if You Can
A great way to deal with the issue of drafty new windows is to have a comprehensive home energy audit performed.
An energy audit includes a blower door test. A blower door test is an air leakage test on your house. It is a large fan that pulls air out of the house. When the air leaves at the front door new air replaces it from the holes and cracks around the house due to the negative pressure it creates.
A great energy auditor will take you around so you can check the windows as well as other common sources of home air leakage so you can judge for yourself which is worse.
If you decide not to have an audit then you can follow additional guidance about how to seal up your home and do some things yourself.
Then, you can target the areas of the home that are leaking the most. Soon you will be on the path to a more comfortable and less drafty home!
Do It Yourself Tips
It an energy audit is not an option and you are looking for effective ways to reduce drafts, you can try these things:
-Seal can lights (recessed lights) from inside. Watch how:
-Go to your local hardware store and pick up a can of one-part spray foam and find some of the easy to reach cracks and crevices at the basement rim joist.
I would like to hear your comments about this article. Feel free to post something below...