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Example of the importance of weather-sealing a house
Posted by: deckeda
Date: November 24, 2021 08:36AM
Last year I began to frame the basement here. It's an old house with cinder block foundation. Previously the cinder block had been sealed and continues to be dry everywhere.

But they never sealed the sill plate nor rim joist to the foundation. All they did was shove pink insulation in the rim joist cavities, which did nothing but ruin the insulation. But this was common "building science" for many years before the importance is keeping AIR out was fully understood (air carries WATER ... always.)

So before I began framing I pulled away the exposed insulation and vacuumed the bugs. Some rim joist cavities had been home to hundreds to lady bugs and very small snakes. Wasps or mud-daubers were basically a daily occurrence in summer. And all hidden from view because of the warm fiberglas nest.

Oh, and let's not forget the mice. They walked right in the numerous vents (one can be seen in the corner of my first picture before I sealed it shut.) I have one final pest that has yet to be tested, but stink bugs are not active in winter.

I packed each cavity with foam board, in my case 1 1/2" XPS. This is unfaced, closed-cell foam with a 7.5 R rating. There are many other options and design choices depending on the circumstances. And then you seal the edges. Airtight. And then you add additional insulation of whatever kind to that to fill in the cavity. Rim joist areas of houses are among the very worst areas where cold comes in. The wall below it will be cold and damp if you don't correct it up top first.

Because spray foam is truly evil to work with and because this basement is still over-filled with crap, getting access to the sill plate / top of foundation wasn't easy when this wall was sealed months ago. We were about to start paneling the last wall yesterday but I wanted to check the sealing. Working in winter really helps, because all you do is stick your hand up there and note the temp. We had some isolated cold spots, and one corner was so cold the cement wall was very cold. Condensation was occurring, with water running down the wall.




Look at the 5 sections of the wall, from left to right. The two sections in the corner were very cold and wet. The middle one (fully insulated, where the step ladder is) was OK. The one just to the right was also cold. The one next to it (last section without insulation, with clamp resting) was nearly room-temp. This is why I say you gotta seal out the air. Even with no insulation the basement last year was much better because I'd sealed it first. (Or so I thought ... )

Here's a picture of what I'm talking about:



See how the foundation top is exposed? Cold air was coming through, and falling down the surface of the interior wall. This is also why you should push insulation flat against the wall so that the cold air can't easily fall to the bottom and cause moisture problems later. We had done that but the water still came down because the air leak was huge. This isn't pink fiber, it's mineral wool and wasn't damaged.

This sill plate should have a barrier between it and the concrete, but with an 80-yr house ... not so much. Then again they should not have used 2X6 sill plates on top of 8"-wide concrete. The good news is that this not pine.

And the result ... We splooged half a can of more Great Stuff at the sill plate/rim joist holes and other areas identified last night and the wall is BONE DRY this morning and the surface is room temp, without any insulation.
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Re: Example of the importance of weather-sealing a house
Posted by: modelamac
Date: November 24, 2021 08:48AM
Correcting another's mistakes without a complete tear-down & re-build can be a nightmare. You are spot-on re starting the work in the winter.



Ed (modelamac)

I think I will just put an OUT OF ORDER
sticker on my head and call it a day.
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Re: Example of the importance of weather-sealing a house
Posted by: mattkime
Date: November 24, 2021 09:36AM
Thats exactly what I need to do with my sill plate. Hopefully I'll get to it this winter.


>Because spray foam is truly evil to work with

Yes, I made the exact same determination. Spray foam works during construction or perhaps if you can empty your basement AND provide good ventilation. I honestly wonder how a pro would deal with the lack of windows.







Edited 1 time(s). Last edit at 11/24/2021 10:54AM by mattkime.
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Re: Example of the importance of weather-sealing a house
Posted by: deckeda
Date: November 24, 2021 10:35AM
After this basement, I'm done with this adventure. We rent from my inlaws and this is all my donation. The house also has a smaller crawlspace portion that isn't terrible (no standing water) but also isn't sealed at all. Air breezes in and enters the living areas and so on. But I'm not going to tackle that.

Before I started, the basement had 3 noisy old dehumidifiers that ran all year. One on the floor and two installed on walls. Now we never run them. Here's one in the laundry/utility section:



Yep, they plumbed it into the drain. Rather sophisticated if you ask me. Another wall-mounted unit was plumbed with a garden hose poking through the cement wall before we hydro-sealed that.

And here's the overview of vented spaces.



Sill plate and rim joist sealing aside ... I would wager every new home with a crawl space uses foundation vents because that is far cheaper than properly sealing an interior space. The only difference between a crawl space and a basement is what's on the floor.

The "gotcha" is that you must do one or the other. Vented crawl spaces are a good idea in open homes that are no longer built (!) Air flows in and "washes away" moisture out the other end. But as soon as you add HVAC and some weather sealing here and there, having holes in your foundation becomes a really bad idea.

Similarly, if you seal up vents without allowing moisture to get removed or blocked (like in a crawl space that's not been encapsulated) you've just made it worse. It's OK to do this in a basement, because the moisture from the cement slab exits via the HVAC.

Crawl space companies charge several thousand dollars to correctly retrofit crawl spaces, despite this being something that could be done far cheaper if only the builder did it instead. This scenario will likely never change without regulation, assuming anyone cares. Housing costs will go up, but so will health.
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Re: Example of the importance of weather-sealing a house
Posted by: lost in space
Date: November 24, 2021 10:59AM
Good work! When I had my shop built, I insulated and sealed *everything* including vapor barriers on the floors, walls and ceiling, just under the drywall. It's astounding how easy it is to keep the temperature and humidity under control. Just the heat off my body can bring the temp up a degree or two, humidity as well.



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Re: Example of the importance of weather-sealing a house
Posted by: mattkime
Date: November 24, 2021 11:03AM
>Before I started, the basement had 3 noisy old dehumidifiers that ran all year.

Were they particularly old? The previous owner of our home ran two giant dehumidifiers which we replaced with a single modern $200 dehumidifier.

I doubt I'd succeed in sealing up the basement to the point that the dehumidifier wouldn't be needed. If nothing else, our old floors are likely porous enough to let humid air in.



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Re: Example of the importance of weather-sealing a house
Posted by: graylocks
Date: November 24, 2021 12:10PM
deckeda -

you da man! I am hijacking your thread for your input on my own current insulation quandary. A few weeks ago I posted this thread about my Weeping Walls.

i've taken in three quotes. All say the insulation is not wet but two see evidence of mold and vermin feces so they want to suck it all out, airseal the attic, and blow in fiberglass to R49. Cost is about 5K. It costs about as much to remove the old stuff as to put in the new.

The third company sees no evidence of mold and very little of vermin poop. They propose to keep the insulation that is there (which they identified as the fiberglass i had blown in in 1995 and cellulose underneath that), move around what's there by sections so they can airseal, and then blow fiberglass on top to the code required R38. This company feels the weeping walls are from boric acid leeching from the cellulose and they also directly addressed my humidity issue by looking at my crawl space and recommending foaming the house underfloor. This possible solution was mentioned to me by a salesman at a high end guitar store who was having similar issues with humidity in his own home. Just doing the attic comes in at about 3.3K. The crawl space is another 5K and i don't think I want to go there at this time.

What do you think? Do I believe the quotes wanting to remove the insulation because of mold/feces who would make more money if I agree? Do I go with the less expensive quote that doesn't remove what's up there which seems more environmentally responsible but risk that they are missing a possible health concern?



"Success isn't about how much money you make. It is about the difference you make in people's lives."--Michelle Obama
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Re: Example of the importance of weather-sealing a house
Posted by: deckeda
Date: November 24, 2021 12:29PM
Quote
mattkime
>Before I started, the basement had 3 noisy old dehumidifiers that ran all year.

Were they particularly old? The previous owner of our home ran two giant dehumidifiers which we replaced with a single modern $200 dehumidifier.

I doubt I'd succeed in sealing up the basement to the point that the dehumidifier wouldn't be needed. If nothing else, our old floors are likely porous enough to let humid air in.

Yes, several decades old. And sure new ones would be quieter but that wasn't the goal. You might surprise yourself once you get started. Some areas will be hard to access but if you can see the types of cracks and gaps I've shown here you'll succeed. If your basement is unfinished you're good, and the flooring won't matter for what I've been talking about.
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Re: Example of the importance of weather-sealing a house
Posted by: deckeda
Date: November 24, 2021 12:52PM
Quote
graylocks
deckeda -

you da man! I am hijacking your thread for your input on my own current insulation quandary. A few weeks ago I posted this thread about my Weeping Walls.

i've taken in three quotes. All say the insulation is not wet but two see evidence of mold and vermin feces so they want to suck it all out, airseal the attic, and blow in fiberglass to R49. Cost is about 5K. It costs about as much to remove the old stuff as to put in the new.

The third company sees no evidence of mold and very little of vermin poop. They propose to keep the insulation that is there (which they identified as the fiberglass i had blown in in 1995 and cellulose underneath that), move around what's there by sections so they can airseal, and then blow fiberglass on top to the code required R38. This company feels the weeping walls are from boric acid leeching from the cellulose and they also directly addressed my humidity issue by looking at my crawl space and recommending foaming the house underfloor. This possible solution was mentioned to me by a salesman at a high end guitar store who was having similar issues with humidity in his own home. Just doing the attic comes in at about 3.3K. The crawl space is another 5K and i don't think I want to go there at this time.

What do you think? Do I believe the quotes wanting to remove the insulation because of mold/feces who would make more money if I agree? Do I go with the less expensive quote that doesn't remove what's up there which seems more environmentally responsible but risk that they are missing a possible health concern?

Go up and look for yourself? It might have been helpful if each had taken a few pictures while they were up there. If you see a few random dirty areas and evidence of mice don't worry. If you see black all over the insulation rip it out. There should also be a mold test available if a visual inspection isn't conclusive.

If I'm understanding your quotes, all 3 want to seal up there after moving or removing insulation out of the way. Sounds good, but it's also my understanding you can't necessarily seal underneath a roof unless you have a ridge vent? I'm sure they're talking about sealing off the upper interior ceiling from the bottom of the attic, which yes IS a goal.

Address the roof first and do the crawl space later, with a crawl space specialist. Foaming in the crawl space sounds wrong on several levels, especially if their idea of sealing/insulating only squirts foam on the underside of the joists. That's not enough, because the ground must be encapsulated also or else the new insulation will just collect mold. That's actually no different than when people put pink insulation in joists and do nothing else. They become a sponge.

Some crawl spaces will also forever need a dehumidifier installed. If you have trouble sleeping at night, pore over Crawl Space Nija's channel: [www.youtube.com]
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Re: Example of the importance of weather-sealing a house
Posted by: mattkime
Date: November 24, 2021 12:55PM
graylocks - I think local knowledge is very important in cases like yours. Neighbors can be a huge help since they're likely dealing with the same landscape conditions and building practices. Often times they just go with who they trust, even if thats just based on a gut feeling. In your case, finances might come into play too, keeping in mind you might need to have all the work done to fix the problem.

You could ask to see evidence of mold and vermin. The problem with mold isn't directly the mold but air passing through.



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Re: Example of the importance of weather-sealing a house
Posted by: btfc
Date: November 24, 2021 01:00PM
“ What do you think? Do I believe the quotes wanting to remove the insulation because of mold/feces who would make more money if I agree? Do I go with the less expensive quote that doesn't remove what's up there which seems more environmentally responsible but risk that they are missing a possible health concern? “


The advice from the third guy sounds sensible, but I’d get confirmation; perhaps a home inspector, who wouldn’t have the same financial stake as the others.
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Re: Example of the importance of weather-sealing a house
Posted by: graylocks
Date: November 24, 2021 01:04PM
Quote
deckeda

Go up and look for yourself? It might have been helpful if each had taken a few pictures while they were up there. If you see a few random dirty areas and evidence of mice don't worry. If you see black all over the insulation rip it out. There should also be a mold test available if a visual inspection isn't conclusive.

If I'm understanding your quotes, all 3 want to seal up there after moving or removing insulation out of the way. Sounds good, but it's also my understanding you can't necessarily seal underneath a roof unless you have a ridge vent? I'm sure they're talking about sealing off the upper interior ceiling from the bottom of the attic, which yes IS a goal.

yes, the air sealing they are talking about and which is now required in new construction is the bottom of the attic or the attic floor i guess. they did take pictures and I will look more closely and poke my head up there myself. Quote #3 who saw little evidence of it said mold would be orange or green; the black mold we hear about is grease based and would be found in structures where chicken mcnuggets were being cooked all day. didn't google that to check but i will.



"Success isn't about how much money you make. It is about the difference you make in people's lives."--Michelle Obama
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