Excellent Airtightness Makes Doors Hard to Open
tech1234
| Posted in General Questions on
Hi everyone, I recently finished my PGH build and the house is very tight. (0.6 ach50) the exterior doors are difficult to open and close because of the air tightness. (I know this because if I open a window they are easy to open and close)
(erv balanced ventilation)
Has anyone else experienced this?
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Replies
Well I would say run a slightly imbalanced ERV but since these are probably inswing doors the only way to make them easier to open is to de-pressurize the house which is not the type of pressurization you want. Are you sure the house is balanced pressure with the atmospheric pressure?
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An ERV running unbalanced wouldn't really help here, since it would be holding the house at a constant positive or negative pressure with respect to the outdoors. Depending on the swing of the doors, that could potentially make things worse.
What would probably help would be an outside air vent somewhere with a damper installed "backwards", allowing air to ENTER from outdoors. In the normal situation, with the doors closed, the small spring on the damper would keep it closed, keeping your home sealed. You could run your ERV in the normal balanced mode. When a door opens, the low pressure created would open the damper on that vent, allowing a burst of makeup air to enter to relieve the pressure on the door, making it easier to open. That's the simplest way I can think of to deal with this problem while still maintaining the excellent air sealing of the home.
Bill
Bill,
Is this something that occurs in other very tight houses? I can't remember it ever coming up before.
My house (0.5 ACH50) does this, but it's only a minor nuisance. At the first instant of coming into the house, it's easy to tell if a window is cracked somewhere in the house because the "cushion" behind the door isn't there. It's a little more obvious when leaving, because we're used to pulling the door shut with some aggression to overcome the vacuum. If a window is open the door ends up slamming closed forcefully. It can be hard on a marriage.
On a smaller scale, the same principle is in play anytime a storm door is installed; you have to calibrate the pneumatic closer to work smoothly either when the main door is closed or open. It's a dramatic difference.
Andy, That is the exact effect I am getting... you get used to the extra effort to open or close the door and then the one time my wife has a different door open letting a dog out or something I unknowingly slam the door
You and me, we tight. #greenbragging My house is so tight the toilet bowl water sloshes when I rush in the back door. My house was so tight at dry-in that the plumber's farts took a full day to dissipate.
Andy, its a new format for jokes... instead of "you might be a redneck if..." ... "you might be overly obsessed with airtight envelopes if..."
probably a lot less relatable though
Ya Bill, my engineering brain has been kicking around an idea of building a "2 way" damper that is sealed at rest and swings in or out when the doors are opened or closed. probably held with an adjustable detent or spring. I wonder if wind would be an issue though as i'd bet the door action and the wind are similar forces.
tech1234,
I knew it was a problem with vehicles, but not houses. GM pickups have an opening with a rubber flapper between the cab and bed. Rats used it to enter a neighbour's new truck and ate his seats.
Most vehicles have a pressure bypass like that, but it's usually less visually obvious on cars and SUVs than pickups.
If you want to make it swing both ways, I'd use a pair of magnets instead of a detent. Magnets won't wear out over time, and they'll give you a very smooth operating action as they get close or seperate. The problem would be the seal/gasket for the damper, which will be harder to design to work reliably over time. You'd probably have better luck with two standard dampers in parallel, each "facing" the opposite direction. This way one handles air coming in, the other handles air coming out. You could adjust spring tension to control how much resistance the damper offered to dial in the response the way you want.
As an engineer, I'm now seeing control theory for over and under damped systems coming into play with doors on very tight houses. I would not have ever expected to think about that :-D
Bill
Malcolm, I have not seen this myself in a house before. I've seen issues with fireplaces and insufficient draft, so a window would need to be opened to get the fireplace to work, but I've not seen an issue with doors before. I've only seen doors "stick" from air tightness on things like large walk-in freezers and cleanrooms before. Both are relatively small (usually) and VERY tightly sealed special-purpose spaces.
With houses sealed this tightly, I would absolutely want AT LEAST TWO CO2 level alarms, with battery backup. While superior air tightness may be nice from an energy efficiency standpoint, it's very not-nice for the occupants health if anything goes wrong with your ventilation (i.e. HRV) system and no one notices...
Bill
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Is the .06 ACH50 number a typo?
A very tight house would be .6 ACH50
Walta
Yes sorry that was a typo. I'll fix it
Maybe you could make some sort of pressure buffer with an elastic membrane that is couple to exterior/interior. It shouldn’t need that much make up air should it? It would at least be fun experiment and you could always just turn it into traditional damper if it didn’t work.
Edit: alternatively you could install a mua that has a pressure switch, perhaps it’s that your house is always slightly out of balance with exterior and something like the broan pressure switched air damper would reduce the issue.
0.6ACH isn't exactly what I'd call very tight. That's the minimum standard for every Passive House. My house is 0.2ACH and I don't experience what you're describing.
It will be more noticeable in smaller volume homes, since with smaller air volumes there is less air volume to "buffer" small pressure changes. The air in the home will act a little like a spring, and the more of it you have, the softer the air "spring" will feel when opening a door. Larger homes would need to be tighter (in terms of ACH50 numbers) to have the same effect on doors.
Bill
Yes, my entire enclosure is barely 10,000 cubic feet--small and tight. I'm not convinced a damper would be effective in a practical sense. The effect is noticed only in the last, say, inch of travel of an exterior door... maybe 1/100 of a second. Could a damper react quickly enough to matter? Maybe we should just gently close our doors and not worry too much about it.
Yeah, even what we consider tight houses aren't that tight.
Let's imagine a house that is 2,000 SF, a volume of 20,000 cubic feet. At 0.6 ACH that's 12,000 cubic feet per hour, or 200 CFM at 50 Pascal.
A typical front door is about 20 square feet. Imagine that once it's open 3" the size of the opening overwhelms any tightness of the house and it swings freely. To open it that 3" you're moving a triangular wedge of air that has an average thickness of 1.5", or 2.5 cubic feet of air. Assume that takes one second, so that 2.5 cubic feet per second you're moving, or 150 CFM -- or about 3/4 of the amount being moved at 50 Pascals. Assuming that air leakage is linear with pressure, you would be changing the pressure in the house by 37.5 Pascals.
That's equivalent to 0.0054 PSI or 0.77 pounds per square foot. With a 20 square foot door that's a total load of 15.6 pounds. I guess that's noticeable.
I've only personally every seen one time where a door was pulled shut by air pressure suffiently that it was diffult to test. This was for a generator room at a customer site, and the commercial 3x8 foot door was HARD to open. What happened was the generator started for an exercise run, but the air intake louvers for the room handn't opened. The radiator fan (~40,000 CFM or so, maybe more), and the turbo on the ~900 HP diesel engine, were pulling enough vacuum in the room that it was hugely difficult to get the door open, and the gasket seal around the door was whistling. I was actually suprised the engine was running OK, but it was. I'm sure there was no dust left in any air leaks in that room! Imagine a blower door test with a 6 foot diameter fan powered by the equivalent of about a 30 HP motor...
Anyway, I've sometimes seen doors be noticeably "sticky" when first opened or closed in things like walk-in freezers and clean rooms, both of which are typically air sealed far better than a house. It feels like extra durable weather stripping when you do the last inch or two of door movement in and out of the jam in either direction. I'd expect that a simple damper would alleviate that pressure, and it would be easy to test: put a simple dryer vent with a built-in damper in a window, tape it up with some thin plywood and painter's tape. Set it for the damper to open INWARDS, towards the interior of the house. Now try opening the door. If the door opens easily, the vent probably worked. A helper should see the damper in the vent briefly open at the instant you break the seal of the weatherstripping on the door too. If that test shows the vent works, then you can decide if you want to build in a permanent solution.
Bill
This house is 900 sqft per floor. 2 floors (no basement). 2 of the 3 exterior doors lead to enclosed spaces outside the envelope (front porch and breezeway) both of those spaces are also very airtight. The relatively small air volume and attached airtight spaces are probably exaggerating the problem. Things are slightly better when windows are open in the breezeway and porch.
Also likely the blower door number is lower than the tested 0.6 ach50 as the blower door was done by the insulation contractor that I had a lot of issues with and I had to point out many issues with there blower door setup.
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That happened on one project I designed, where the builder got it down to 0.12 ACH50. (Not a typo.) We included a small damper for passive makeup air but it wasn't enough, especially if the dryer was running. The dryer was a conventional, exhausting type; I was not able to convince the owners to buy a ventless dryer. The house is about 2200 sq.ft. with a full basement, with over 35,000 cubic feet of air, so it was surprising that a 125 cfm vent would make a noticeable difference.
I have never experienced the hard-to-close-door situation in the many Passive Houses I've been in.
Did that builder get down to 0.12 ACH50 using what I'd call "conventional means" (careful use of caulk and canned foam, good tape details, etc.), or did they use Aerobarrier? I usually think of Aerobarrier as a way to fill all the little tiny leaks that would otherwise be missed. Just curious if you got down to really tight levels without going that route.
Bill
Bill, this was before Aerobarrier was even available. They used various Pro Clima tapes, membranes and sealants. I had only spec'd 1.0 ACH50 and maybe the doors would have operated better if they had stuck to that, but at the time it was probably the tightest house in Maine!
Has a third party come in to commissioned your ERV to confirm it is balanced, at each diffuser?
Have you been changing your filters to ensure the ERV stays balanced?
Do you feel or hear a hiss of air when you open the door?
In my non certified Passive House with 0.3 ACH I can tell when one of my filters is clogged as my door is hard to open. If the ERV is balanced then it will not make a difference to opening or closing the door. If it is out of balance it will.
Frank, I have a Broan AI series ERV that is self balancing. (In theory at least)
I am very diligent about keeping my filters clean.
Gonna say it again, because it's incredibly aggravating.
GBA/Taunton Staff: Please stop editing post titles after they are created.
Patrick, as someone mentions whenever this comes up, GBA needs to make money in order to keep the doors open, and by changing the title they get better SEO results--more people searching online will see the question, attracting them to GBA and improving their advertising numbers. It's an unfortunate fact of modern, online life. When the title change is inaccurate, that's another thing, but they usually get it right.
100%. So annoying to look back for a thread to check on an answer only to have the title changed and not be able to find it.
If Kylie insists on changing the titles, can we at least compromise with something like:
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This way we can still find it and the web crawlers of the future can get their shiny new SEO title.
The original title is still in the address bar. It doesn't help much in finding a thread but it does let you see what it was originally.
I'd buy an electric radon tester if my house were that pressurized.
We have liked ours: https://www.amazon.com/Corentium-Detector-Airthings-223-Lightweight/dp/B00H2VOSP8