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Old 06-04-2019, 11:07 AM   #1
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Air Sealing - New Construction


I'm about 95% done the build of my new house. To get a CO, I need to have a blower door test done sooner rather than later. What I'm wondering is if any of the unfinished work is likely to affect the test results. Specifically, I don't have all my window trim up yet. I wouldn't think the wood trim would really do much, and each window was spray foamed around the perimeter, but didn't want to waste money getting it tested if the lack of trim is going to cause a leak.

Last edited by nobbyv; 06-04-2019 at 11:20 AM.
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Old 06-04-2019, 05:42 PM   #2
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Re: Air Sealing - New Construction


We're certainly going to need more details than that for anyone to hazard a guess.
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Old 06-04-2019, 08:20 PM   #3
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Re: Air Sealing - New Construction


if you do a really good job sealing around windows, electrical penetrations i don't think there should be a big difference.

*if you have an interior vapour barrier make sure the seams are tuck taped and it's sealed to the framing at top and bottom.
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Old 06-05-2019, 10:26 AM   #4
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Re: Air Sealing - New Construction


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Originally Posted by stick\shift View Post
We're certainly going to need more details than that for anyone to hazard a guess.
Thought my post was pretty clear, but maybe not: does interior window trim have any effect on air sealing?
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Old 06-05-2019, 10:38 AM   #5
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Re: Air Sealing - New Construction


In most cases not.

Now, if you can tolerate our interest we will ask some questions that may help you pass that blower door test. A standard framing approach will not pass (IMO) so what have you done during the assembly to improve the sir sealing. We have the window information but I', looking for where sealing efforts were applied to sheathing, sill, rim, top and bottom plates, along with all man made penetrations.

Inexpensive infrared cameras are more common now and night temperatures are often cool enough to give a cold signature. if you have access or rent as camera on a cold night with a big exhaust fan in a window you may be able to spot some of the problem leaks, before paying for the blower door test.

if the blower door company will cooperate it is often very beneficial to chase leaks while the blower is running.

Good luck.

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Old 06-06-2019, 10:35 AM   #6
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Re: Air Sealing - New Construction


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We have the window information but I', looking for where sealing efforts were applied to sheathing, sill, rim, top and bottom plates, along with all man made penetrations.
Gotcha, understood, and my apologies to stick\shift if my reply sounded rude. I wasn't understanding what he was asking. My mistake.

To get a feel for the layout: its a two-story house with a walk-out basement and attached garage, and a "cold" roof attic. A summary of what sealing has been done thus far:

1) Top two floors' walls are dense-packed cellulose w/ no vapor barrier. Basement is fiberglass w/ vapor barrier sealed top/bottom. Attic is about an R-50 of cellulose at current insulation depth
2) All top/bottom plates sealed at floor/ceiling w/ poly sealant
3) Any double/triple exterior-wall studs as well as window/door jack studs and headers sealed
4) Dow sill seal used on sill plate
5) All exterior-wall electrical boxes spray foamed behind them
6) Exterior sheathing seams are all taped (ZIP System)
7) All can lights protruding into the attic are airtight style, with the cans properly adjusted to sit flush w/ the drywall
8) All electrical/plumbing penetrations to outside sealed w/ either spray foam or silicone caulking
9) As mentioned, all exterior doors and windows were flashed on the exterior w/ ZIP tape, then the borders spray foamed from the interior
10) HVAC ductwork appears to have been pretty meticulously sealed, then insulated, then sealed again

A few areas of concern:
1) Have a large gas cooktop that necessitated a large range hood and thus a large diameter duct to vent it (10" round). The hood itself has a damper, and the vent wall cap I installed outside has a damper, but I am still concerned due to the diameter. Should I be?
2) House has a 42" wood-burning prefab fireplace WITH an outside air supply. Outside air supply line was silicone caulked at the outside wall penetration. Outside air supply has a damper, but I am not sure how great it seals. Plus, there's the normal chimney damper at the top of the firebox
3) Clothes dryer vent w/ damper
4) Most interior window trim isn't installed yet (seems like probably a non-issue)

I think we have an infrared camera here at work, so I will plan to try and run the test on my own beforehand. But is there anything else that's screaming "Problem" from what I have here?

Thanks!

Last edited by nobbyv; 06-06-2019 at 10:47 AM.
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Old 06-06-2019, 11:02 AM   #7
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Re: Air Sealing - New Construction


The air supply damper needs to open inward so is subject to inward pressure at all times. Hard to improve.

Dampers are always an issue but necessary.

One thought. Sounds like you have gone past the tipping point and have the house "too tight" which is good. At that point you start adding intentional air leaks to maintain air quality. But there's a difference between the air leaks you sealed and the new intentional fresh air, the new air follows controlled paths and is not depositing moisture and pollutants inside your walls.

When they do the blower door test you will want all of their numbers, house volume, ACH (air changes per hour), CFM50 (leakage at -50 Pascals), Duct leakage and leakage to outside, along with some searching for major leaks while the fan is running. Hopefully they have an Infrared Camera, but difficult to get good images when it is warm outside, winter does great.

The search for temperature signatures can be done inside or outside. If you add heat inside and set the fans to blow inward warm air will show up outside. Another example of testing late when it is colder out. Also dampers that open outward will show up.

Bud
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Old 06-06-2019, 11:21 AM   #8
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Re: Air Sealing - New Construction


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Originally Posted by Bud9051 View Post
The air supply damper needs to open inward so is subject to inward pressure at all times. Hard to improve.
It does open inward, so that's good at least.

Quote:
Originally Posted by Bud9051 View Post
One thought. Sounds like you have gone past the tipping point and have the house "too tight" which is good. At that point you start adding intentional air leaks to maintain air quality. But there's a difference between the air leaks you sealed and the new intentional fresh air, the new air follows controlled paths and is not depositing moisture and pollutants inside your walls.
We did opt to add a humidifier to the HVAC system, but I passed on the fresh air recovery unit that my HVAC installer recommended until I could see the results of the blower door test. You may be right; it may prove necessary.

Quote:
Originally Posted by Bud9051 View Post
When they do the blower door test you will want all of their numbers, house volume, ACH (air changes per hour), CFM50 (leakage at -50 Pascals), Duct leakage and leakage to outside, along with some searching for major leaks while the fan is running. Hopefully they have an Infrared Camera, but difficult to get good images when it is warm outside, winter does great.

The search for temperature signatures can be done inside or outside. If you add heat inside and set the fans to blow inward warm air will show up outside. Another example of testing late when it is colder out. Also dampers that open outward will show up.

Bud
Good info, thanks!

Last edited by nobbyv; 06-06-2019 at 11:28 AM.
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