Ashley P

home insulation

24 posts in this topic

Would ya'll help me scratch my head about insulation? 

The old part of the house has 2x4 walls with no insulation.  They are fairly air tight due to being wrapped in 1x12 tongue and groove boards covered in tar paper. 

My basement addition is about 2.5" wider than the house siding due to the width of the insulated concrete form blocks.  Thus, I figured I'd pull off my old vinyl siding and fur out (with pine lumber) about 2.5" to get new siding to match the basement.  That gives me 2.5" to insulate under new siding and 3.5" of "inside" the wall.

 

My first thought was to put about 2.5" of rigid board insulation behind the new siding.  Caulking/gluing every seam would make it very air tight.  While the old vinyl is off, drill holes and blow cellulose into the walls.

Then I got to thinking about interior moisture not being able to escape the rigid board insulation.  I could end up with a huge moisture problem at the 1x12s.  Last years single digits for a week proved that there is not much of a moisture barrier as I had some icicles on my siding that formed from moisture coming through the wall (at least that seemed the only possible source).

 I'm crosseyed thinking about moisture control .

Any ideas?

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I think you are. In a recent Habitat build we did we were wrapping up the exterior. To say this house was sealed up would be an understatement. I mean, this house was sealed. I htink I could have put 100psi in that house and not had a pinhole leak.... You get the idea. I don't htink you can go overboard on insulation. More is better and more is best. It works for your advantage in every season. Only downside is the up front costs, all of which are recouped over the years.

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On one hand, I totally agree on the value of insulation and sealing things up.

On the other, sealing things up is a double edged sword.  While it severely restricts moisture entry, it also severely limits moisture exit.   If the Habitat house was sealed that tight, what methods of moisture control were used?  What type(s) of insulation were used?  Oh, how was it sealed?

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13 hours ago, JohnC said:

Check the house for radon often. :yes:

speaking of.. my dentist is battling lung cancer due to radon...they think. he's never smoked and grew up in a basement house. That seems to be the only thing they can tie it to.

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10 hours ago, Raceall said:

You will have to make sure that you have a proper amount of air exchange, with a really tight house, or else you will have major mold issues.

And how does one figure that "proper amount"?   Your house is about as tight as one can get with spray foam everywhere....how's that have any exchange?  Is it open cell?

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23 hours ago, Ashley P said:

On one hand, I totally agree on the value of insulation and sealing things up.

On the other, sealing things up is a double edged sword.  While it severely restricts moisture entry, it also severely limits moisture exit.   If the Habitat house was sealed that tight, what methods of moisture control were used?  What type(s) of insulation were used?  Oh, how was it sealed?

You cannot make the house too tightly sealed. The better it's sealed, the more YOU control the ventilation. You need ventilation of course, but it shouldn't be coming through the walls, outlets, door sills, siding, etc. You control where it comes from and how much will come through. How much do you need? I guess the best answer is "It depends". But starting with the ideas laid out here, you can go forward with your sealing up and insulating of the house. Study how much ventilation you'll need and how you will accomplish that while you're waiting on the spray foam to dry.

Also: consider your current vents. If you have gas water heater, dryer, bathroom fans....  All of those move air out. So you need a way to get new air in. That's what you can control. You only need a "passive" vent, you dont need a fan to bring air in. But, you need the vent(s) to be able to equal all your other so you don't get a backdraft. You don't want to run the dryer and bathroom fans and end up pulling air in through the hater heater vent. 

 

Am I making any sense here?

Edited by Disney

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Yes, you made sense, but I may not be getting my point across.

Some people will strongly disagree that a house "can't get to tight".  Picture wearing a plastic jacket in the winter:  You'll get wet outer clothes due to the moisture condensing on the plastic.  A house will heat well that way, but might rot out a couple decades later.

That's why I'm curious as to how the Habitat house was sealed.  Some products like Tyvek attempt to block all air infiltration, but let humidity pass through.

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33 minutes ago, Ashley P said:

Yes, you made sense, but I may not be getting my point across.

Some people will strongly disagree that a house "can't get to tight".  Picture wearing a plastic jacket in the winter:  You'll get wet outer clothes due to the moisture condensing on the plastic.  A house will heat well that way, but might rot out a couple decades later.

That's why I'm curious as to how the Habitat house was sealed.  Some products like Tyvek attempt to block all air infiltration, but let humidity pass through.

I believe you're missing @Disney point.

Tight house no vent = bad

tight house vented how you want/need = good

I'd say there's a good reason why crawl space encapsulation is so popular right now. It's sealed and YOU control the moisture content.

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So, let's say I've got a tight house.  It's wrapped in plastic.  Air cannot penetrate except for the vent.  The vent is in a great location to pull in air that's just the same humidity as the air it's replacing.

Won't moisture still condense on the plastic?   I think it would.

Crawl spaces with moisture control?  How?   (Really, just the airflow is controlled, right?  That's kinda the basis for my confusion:  airflow vs moisture control.)  (BTW, so far my "crawl space" is incapsulated VERY well! lol)

 

 

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2 hours ago, Ashley P said:

So, let's say I've got a tight house.  It's wrapped in plastic.  Air cannot penetrate except for the vent.  The vent is in a great location to pull in air that's just the same humidity as the air it's replacing.

Won't moisture still condense on the plastic?   I think it would.

Crawl spaces with moisture control?  How?   (Really, just the airflow is controlled, right?  That's kinda the basis for my confusion:  airflow vs moisture control.)  (BTW, so far my "crawl space" is incapsulated VERY well! lol)

 

 

No, moisture won't condense inside the plastic if you are venting and have good working HVAC. 

Think about summer heat. You're sweating due to the humidity. Then you stand in front of a fan moving air around you that is the same humidity. 

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Disney, I'm scratching my head.   Let me ask you this:  Why does condensation form on my single pane windows this time of year?   I think that's a good example of what I do not want in my wall.

(Let's stay on winter heating since I can't even figure that out, no sense confuzzing me any more.)

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50 minutes ago, Ashley P said:

Disney, I'm scratching my head.   Let me ask you this:  Why does condensation form on my single pane windows this time of year?   I think that's a good example of what I do not want in my wall.

(Let's stay on winter heating since I can't even figure that out, no sense confuzzing me any more.)

The condensation forms on your window because it's not insulated enough and the temp drop across the pane of glass is very high.  With the wall structure that is ~6" thick, the temperature gradually increases from outside to inside. The idea is that the the air/insulation space inside the wall stays dry (I believe this is the purpose of the vapor barrier) so there is nothing to condense. 

The air inside air in your house can be humid, but the temperature difference from the living space to the interior wall (across drywall) is very small.  The air inside will hopefully never be as humid as it is outside so no vapor barrier is needed between the interior and the inner wall.

So, the air you are letting into the house via ventilation could be humid, but it's not going to touch a surface that has a high temperature drop.  Localized around or in the vent it might, but in general throughout the house it won't.

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36 minutes ago, Mike said:

The condensation forms on your window because it's not insulated enough and the temp drop across the pane of glass is very high.  With the wall structure that is ~6" thick, the temperature gradually increases from outside to inside. The idea is that the the air/insulation space inside the wall stays dry (I believe this is the purpose of the vapor barrier) so there is nothing to condense. 

The air inside air in your house can be humid, but the temperature difference from the living space to the interior wall (across drywall) is very small.  The air inside will hopefully never be as humid as it is outside so no vapor barrier is needed between the interior and the inner wall.

So, the air you are letting into the house via ventilation could be humid, but it's not going to touch a surface that has a high temperature drop.  Localized around or in the vent it might, but in general throughout the house it won't.

I'm talking about winter conditions, where relative humidity outside is low, and inside is higher (if we want to avoid noisebleeds). (Edit: Inside RH will be lower with heated air.)

I've gotta sit down and read through this later....got an LS with no fire on one bank...which spread to both banks here in the bay..

Edited by Ashley P

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10 hours ago, Ashley P said:

And how does one figure that "proper amount"?   Your house is about as tight as one can get with spray foam everywhere....how's that have any exchange?  Is it open cell?

Generally, air exchanges utilize a damper to allow fresh air to circulate at controlled amounts.  There is no way to completely keep moisture out of a house.  When you get even small amounts of moisture, while circulating the same air without exchanging it for fresh air, the house becomes a peachtree dish for mold.  There are times in the summer when I think that my house might be just a tad too tight.  As far as figuring it, that's not exactly my wheelhouse.  It has to do with amount of cfm, square footage, etc.

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Guys, I may not be clear. Or I'm T-totally retarded about this.  But I'm not talking about the air exchange that happens when a door is opened or an exhaust fan runs.  I'm talking about tiny air and/or moisture movements over the entire wall surface.  Insulation materials provide a resistance to heat transfer and also provide varying levels of water control, call it vapor or moisture control.

I've got a chest freezer that's gotten terribly inefficient because the fiberglass insulation has gotten wet over the last few years. I don't think the insulation got wet from the stuff frozen inside it, rather the warm/moist air worked it's way through the fiberglass over the years and caused condensation.  In my view that's an illustration of what I don't want.

 

Other thoughts, I investigated radon before digging this basement.  I can't remember what I found out because it was not noteworthy.  Maybe that we're low risk and radon must be "trapped" against bare concrete to be forced though?  I've got plastic under my slab with loose rock connected to an open drain.   And lung cancer...my dad died of that and I've inhaled a million CFM of car/truck exhaust, I've welded some, breathed paints, torn down an asbestos sided shed when I was about 10, and sand blasted inside a plastic walled area to save my sand.  Oops, oops, oops, ect.  I'd probably have to huff radon for several years to catch it up to the risks I've already taken. :(

And if Disney wants to tell me how that Habitat house was sealed and insulated I'd be all ears.... :) 

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Habitat house was sealed with plastic, caulk, tape, etc. etc. The whole house was sealed up. We taped and caulked every nook. Of course, there were vents installed. Soffet vents, roof vents, and I think one or two through the wall and it seems to me they had a filter system installed on those two.

Yes, I think you are being retarded about this and for the life of me I don't understand why. It's really frustrating to be honest. 

If you have a different climate inside than outside, you will have the opportunity for condensation. That cannot be avoided no matter how well or terribly it is insulated. You have to use air management to control this so you don't suffocate. The point of all this is to maximize energy efficiency, something you'll understand once you LS swap your van. With the house sealed up tightly, you will still introduce fresh air, but you'll do it in a controlled manner, not just a free-for-all through your siding and doors. Those types of air leaks let our the hot/coll air that you spent money to heat/cool. To keep the environment comfortable, you'll use vents to introduce fresh air as you need.

 

I found something for you to read. https://www.hometips.com/how-it-works/ventilation-systems-house.html

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Disney, what products were used to seal that house? (I'm familiar with Tyvek as an example)  When you say "seal", do you men air sealed, or water VAPOR sealed?  (Tyvek claims to stop air but allow water vapor to pass through.)  I'm willing to bet it was not sealed with a big sheet of plastic which would be the most cost effective sealer available.  If not, why not?  I'm guessing it's to allow water vapor to pass through.  Where am I wrong there?

Sorry to frustrate you (and everyone).  I am also frustrated at what is either my ignorance or inability to get my point across.  (I told you I was crosseyed about it.) :)

Thanks for battling me.  The truth of this SURELY will EVENTUALLY dawn on me...maybe.

 

Moisture control:  I've stopped the rain from falling into the house, I've got a basement that (so far) is bone dry. I'm gonna have exhaust fans in the baths that vent outside, and I want a vent to allow fresh air in (and hopefully filter and possibly condition it upon entry). I want the house to be air tight...but water vapor tight....I don't think so.  I think vapor diffusion is my hangup.  I think being in a climate that requires both heavy heating and heavy cooling muddies the water.    https://basc.pnnl.gov/information/building-science-introduction-moisture-flow

Edited by Ashley P

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3 hours ago, Ashley P said:

Disney, what products were used to seal that house? (I'm familiar with Tyvek as an example)  When you say "seal", do you men air sealed, or water VAPOR sealed?  (Tyvek claims to stop air but allow water vapor to pass through.)  I'm willing to bet it was not sealed with a big sheet of plastic which would be the most cost effective sealer available.  If not, why not?  I'm guessing it's to allow water vapor to pass through.  Where am I wrong there?

Sorry to frustrate you (and everyone).  I am also frustrated at what is either my ignorance or inability to get my point across.  (I told you I was crosseyed about it.) :)

Thanks for battling me.  The truth of this SURELY will EVENTUALLY dawn on me...maybe.

 

Moisture control:  I've stopped the rain from falling into the house, I've got a basement that (so far) is bone dry. I'm gonna have exhaust fans in the baths that vent outside, and I want a vent to allow fresh air in (and hopefully filter and possibly condition it upon entry). I want the house to be air tight...but water vapor tight....I don't think so.  I think vapor diffusion is my hangup.  I think being in a climate that requires both heavy heating and heavy cooling muddies the water.    https://basc.pnnl.gov/information/building-science-introduction-moisture-flow

It was "House Wrap" and not Tyvek that i've seen used many times before. Having not tested it, I would say it was AIR SEALED. 

 

This article shows what all we did. Taped all the house wrap joints, used caulk and foam at every crack and joint. "Sealed" everything.

https://www.jlconline.com/how-to/insulation/airtight-new-homes-top-trouble-spots_o

 

All of this stuff being said....  People lived in houses for a long time without doing any of this. Feel free to have yours drafty if you are worried about it being too tight. I for one wish mine was sealed and insulated better.

 

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Thanks.

I'm not against "too tight" when speaking about air.  I'm gonna caulk every joint from the sill plate to the top plate.  But the reason that house "wraps" are not made of plastic is to allow them to pass water vapor.  Plastic would be "too tight" as far as water is concerned.

My freezer insulation that's failing....it's sure not "leaky" and "drafty"....it's basically a plastic tub wrapped in fiberglass which is wrapped in sheet metal.  Yet it's failing in a way I don't want my house to fail.

And that's a good link.  I wish I'd put some type of air barrier under my sill plate/rim.  It's so much money for so little product...

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