What is "Air Sealing" and do I really need it?

[billconner]

beemerphile in GA with warm side out has it a little easier than us with warm side in. There are methods to seal electrical penetrations but they are laborious. I've kicked around to the idea of a baseboard wire way, and keeping as many switches as possible on interior walls or wireless switches in shallow boxes that dont penetrate the vapor barrier.

 

[yeldogt]

A lot of people think that caulk instead of flashing can keep water out. It is really easy for caulk to crack and no longer keep water out. Proper flashing can keep water out long term.

Caulk will eventually fail ..... one has to look back at historical buildings prior to caulk. What worked -- how did they do it?

They used flashing -- flashing to take water away. Knowing that water will get it --- you give it a pathway to get out. Most contractors never think of flashing a window properly .. the use the flange and never read the directions.

 

[yeldogt]

beemerphile in GA with warm side out has it a little easier than us with warm side in. There are methods to seal electrical penetrations but they are laborious. I've kicked around to the idea of a baseboard wire way, and keeping as many switches as possible on interior walls or wireless switches in shallow boxes that dont penetrate the vapor barrier.

That's why I switched to closed foam years ago. I can see using Rockwool for a utility building ... over using fiberglass batt for anything other that sound for interior walls. With foam -- it's done. a

 

[danski0224]

Caulk will eventually fail ..... one has to look back at historical buildings prior to caulk. What worked -- how did they do it?

They used flashing -- flashing to take water away. Knowing that water will get it --- you give it a pathway to get out. Most contractors never think of flashing a window properly .. the use the flange and never read the directions.

OMFG.
Did you really say that out loud?

Lack of flashings and reliance on caulking was (is ) a huge contributor to EIFS (Dryvit) building problems.

Unfortunately, there is a big difference between "old world" methods for flashings vs today. The today methods still place a huge burden on caulking as the last resort.

Many do not know the proper way to do it, either.

The boss will be pushing those that may, and not allow the time.

Cheap, fast, good. Pick two.

 

[yeldogt]

OMFG.
Did you really say that out loud?

Lack of flashings and reliance on caulking was (is ) a huge contributor to EIFS (Dryvit) building problems.

Unfortunately, there is a big difference between "old world" methods for flashings vs today. The today methods still place a huge burden on caulking as the last resort.

Many do not know the proper way to do it, either.

The boss will be pushing those that may, and not allow the time.

Cheap, fast, good. Pick two.

That stuff was a disaster --- because of how it was installed.

The number of leaking flanged casement windows at the beach -- maybe all of them? Nail the window and wrap with J channel -- vinyl siding goes up.

 

[billconner]

That's why I switched to closed foam years ago. I can see using Rockwool for a utility building ... over using fiberglass batt for anything other that sound for interior walls. With foam -- it's done. a

Foam is not perfect.

Reason Foam Fails #5: Excessive Shrinkage

Fine Homebuilding, Feb/March 2012 With the growing use of foam plastic insulation in building construction, first in commercial roofing and then too often metastasizing over the entire building enclosure, it is being used increasingly as an air barrier component. This is a problem for many...

foursevenfive.com

 

[u3b3rg33k]

The fact that ventilation is needed does not mean that ventilation by leakage is needed. A building can be vapor-sealed too well, but it cannot be air sealed too well. Intentional balanced ventilation allows you to select the air source and quantity rather than taking it from spidey holes full of mold and rat urine. Balanced ventilation (exhausting and admitting the same amounts of air) allows you to keep the building pressure from going negative. The absence of a pressure drive will keep air from flowing through the spidey holes and also allows the opportunity for heat and humidity recovery if you choose. Other than cost, air sealing is all win.

Any talk of optimal vapor sealing and insulation needs to be done in the context of location. What is required in Michigan will not even meet code in Georgia. The audience of this forum spans all of the thermal zones.

I think people often forget there's a difference between a vapor retarder and a vapor barrier. kraft paper is a vapor retarder, not a vapor barrier - it is somewhat permeable.

a long explanation:

Vapor Barriers and Vapor Retarders — What's the Difference?

www.wrmeadows.com

the gist of it is to me that you want your insulation undisturbed by air movement, and you don't want there to be enough moisture present in your insulation for condensation to occur. so for climates where you "dry to the inside" (anywhere with high humidity and lots of AC use), you need to allow your insulation to breathe inwards, but not outwards.

 

[yeldogt]

Foam is not perfect.

Reason Foam Fails #5: Excessive Shrinkage

Fine Homebuilding, Feb/March 2012 With the growing use of foam plastic insulation in building construction, first in commercial roofing and then too often metastasizing over the entire building enclosure, it is being used increasingly as an air barrier component. This is a problem for many...

foursevenfive.com

Has to be done correctly .... have heard of issues in the cold.

Projects have exposed in many places ... have never experienced shrinkage.

 

[Shovelhead]

Reckon in 30 yrs people will be talking about all the idiots who used spray foam and fresh air ventilaters in their igloo cooler homes. LOL

I'd say most important thing to consider per individual is how much your home is worth and how long you intend to live there.
We built a home 33 yrs ago. R13 in the walls, R19 in the attic eventually added blown in insulation on top of that, just because we replaced the roof . Once.

Moderate to low electric bills and suited my family just fine. That was with single pane contractor grade aluminum windows. Since replaced with double pane.

I understand technology and building methods improve over time, or they should.
But I also think there's a lot kool aid drinkin going on with some of these ideas for the average Joe.

Your money, your choice.
It is all pretty confusing and conflicting to me.

 

[toyotadriver]

Houses used to leak so much that they didn't need any mechanical ventilation. It leaked in and out. Energy prices were cheaper then. As energy prices rise (and they are going to rise a lot more), preserving the conditioned space has become more and more important. It's becoming cheaper to preserve conditioned space (more insulation and tighter construction) rather than to keep a leaky and poorly insulated space conditioned. But, as homes have gotten tighter and tighter, the need for mechanical ventilation has become more important.

I'd MUCH rather have a well insulated and air sealed home with mechanical ventilation than a leaky house.

We exceeded the insulation needs for our house and it's such a comfortable house compared to many other houses owned by our friends. And, our heating and cooling needs are FAR less.

 

[u3b3rg33k]

Reckon in 30 yrs people will be talking about all the idiots who used spray foam and fresh air ventilaters in their igloo cooler homes. LOL

I'd say most important thing to consider per individual is how much your home is worth and how long you intend to live there.

spray foam may go out of style, but mechanical ventilation won't - it's the standard in commercial buildings and has been for a while. maybe ICF will be the new thing, or prefab walls. who knows? cement walls don't breathe much.
you can air seal with proper sheathing and tape (the right tape), installing windows properly. It doesn't matter if you put in triple pane windows if wind can blow around the frame.

problem with that kind of thinking is it keeps starter homes expensive to operate. "i won't be there long so why upgrade anything?" then you take it in the shorts when you sell because everything is below par.

 

[Shovelhead]

I wouldn't say my way of thinking is a problem. Maybe not the same as yours or anybody elses, but it's far from a problem for the matter at hand.
A "starter home" is expensive to operate? If that same place had all this high tech expensive insulating and sealing methods would you still call it a starter home? Don't think so. Kids starting out couldn't afford it.

The home we built 33 yrs ago was a Custom Built home from the ground up. It was a financial choice to opt for single pane windows, vinyl flooring in kitchen. Custom built Ash cupboards were more important than the floor at the time.

Each person has a point of view of what is most important for their hard earned dollars.
Honestly, at this point in my life I'd be perfectly fine living in a shed.
More vacations, motorcycle rides, and fishin lures.

Enough of that. Off topic .

 

[beemerphile]

Air sealing is about the most economical thing you can do to a home during construction and damned difficult to do later. In addition to energy savings and greatly reduced condensation potential, the entire pest control industry would die if homes were built properly for pest exclusion. I mean, a few bugs could fly in or ride in on the dog's back, but they wouldn't be running bug convoys though the open places in your home's control layers. The eye of a needle looks like a double door to a termite.

 

[yeldogt]

Building is always about cost .... very few projects have unlimited budgets.

In my case I'm rehabbing an old building or building a new building for my personal use ... I have never bought a "new" house from a developer. Also, all my rentals have been rehabs .... have never built a rental.

There are some things you can look at and make educated choices -- ascetic choices that will affect overall cost but less so on the actual performance of the structure. Insulation and air sealing is not something you can go back and redo. This is a primary part of the building. In an old building you are typically up against construction practices that have no thought to building envelope -- there is no blocking and it's all dimensional lumber vs plywood products .. masonry buildings w/o any insulation are very common ....later you may run into fiberboard type products behind plaster. That's why I moved to spray foam 30 years ago.

I simply would not build with fiberglass batt insulation today -- interior walls only for me. My guess is Rockwool and Zip would be a interesting test case -- even with me never using OSB. I also have no idea what the cost difference between foam/ plywood and Rockwool/ Zip. Rockwool does restrict air movement -- have used in some limited situations.

Part of the build process also depends on regional building practices. Trying to get a ICF or SIP building done in an area where they don't build them is not going to be cost effective. When reading GBA or FH magazine and I see some crazy twin wall or exterior insulation requiring special blocking systems and flashing details --- right .... that's going to work. Who wants to be the first test case on that -- and what is a builder going to charge to do it? That's why I use conventional ways of building .... plywood/ foam and more and more engineered dimensional lumber. I also always use 5/8 rock. Best bang for my buck ,,,,, hard to screw up.

Air sealing is as important as whatever the R value -- maybe more. A small leak can move a lot of conditioned air .... and in a home it's one of the main items that determine comfort.

 

[acer66]

Air sealing is as important as whatever the R value -- maybe more. A small leak can move a lot of conditioned air .... and in a home it's one of the main items that determine comfort.

My next door neighbor grew up in the house I own now which was build in 1901 and some wall covering I discovered during renovations were just news paper and on the outside the walls were just covered with tar wall shingles with no under lament on 1x boards.

He said when he was young they used candy wrappers etc. to seal off all the gaps etc. because all the draft made heating the house almost impossible.

Sure an extreme example but if you do not air seal it you might as well skip insulation.

 

[beemerphile]

Location is everything for insulation performance, but I'll let you know if this Georgia redneck learns anything. I did not want spray foam. My current home build is going to be liquid-flashed Zip +3 sheathing on 2x6 framing @ 24" o.c. with 5.5" Rockwool batts and 5/8" sheetrock. Framing starts in two or three weeks. The insulated Zip (somewhat) breaks the thermal bridging of the studs. 24" o.c. means less studs to detract from the effective R value of the walls. The perimeter of the sheathing and under, between, and outside the sill and top plates will be sealed with acoustical sealant. It will get blower-door tested with leak remediation as necessary, so I expect that it will be a tight structure. Mechanical ventilation will be a conditioning energy recovery ventilator.

 

[mike93lx]

Location is everything for insulation performance, but I'll let you know if this Georgia redneck learns anything. I did not want spray foam. My current home build is going to be liquid-flashed Zip +3 sheathing on 2x6 framing @ 24" o.c. with 5.5" Rockwool batts and 5/8" sheetrock. Framing starts in two or three weeks. The insulated Zip (somewhat) breaks the thermal bridging of the studs. 24" o.c. means less studs to detract from the effective R value of the walls. The perimeter of the sheathing and under, between, and outside the sill and top plates will be sealed with acoustical sealant. It will get blower-door tested with leak remediation as necessary, so I expect that it will be a tight structure. Mechanical ventilation will be a conditioning energy recovery ventilator.

Have you looked at aerobarrier? If I was building now, I'd very likely have them come out. I can't picture a more effective way to seal absolutely everything

 

[beemerphile]

Have you looked at aerobarrier? If I was building now, I'd very likely have them come out. I can't picture a more effective way to seal absolutely everything

Yes, I will consider it if needed after the blower door test. Kind of depends on where the leaks show up. If they can be remedied conventionally, that is what I'll do. The masking and clean-up with aero barrier is not trivial.

 

[mike93lx]

Yes, I will consider it if needed after the blower door test. Kind of depends on where the leaks show up. If they can be remedied conventionally, that is what I'll do. The masking and clean-up with aero barrier is not trivial.

I would assume it would be done at framing. Just mask the windows and then spray

 

[jar944]

Houses need to be able to breathe.

Not randomly through the top plates and band joists.

 

[yeldogt]

My next door neighbor grew up in the house I own now which was build in 1901 and some wall covering I discovered during renovations were just news paper and on the outside the walls were just covered with tar wall shingles with no under lament on 1x boards.

He said when he was young they used candy wrappers etc. to seal off all the gaps etc. because all the draft made heating the house almost impossible.

Sure an extreme example but if you do not air seal it you might as well skip insulation.

Having done quite a few old houses ..... my oldest was an 1810 in Philadelphia -- sealing the leaks is so important. You can make a tight house comfortable w/ radiators in a cold climate ..... not when it's leaking. Prior to WWI all the modest homes in the mid-atlantic often used a fiberboard (thick cardboard) as sheathing with clapboard siding for strength. This cut down on air movement .... I never saw it used on larger homes w/ full second floors. After WWII it got a little better.

 

[larry4406]

My house was built in 1987 and the attic insulation is for sh#t and I can see that none of the framed wall plates are sealed were drilled upward for penetrations (wires, plumbing vents, etc.). One can really feel the air flow thru some of the penetrations.

Insulation company will soon be un-blowing and purging the attic of all of the **** up there (hideous what prior owners did up there).

Once its purged, and all wiring sins identified and fixed, insulation contractor will be applying open cell spray foam to the top side of the ceiling drywall from outer stud wall to out stud wall and will bridge over the 2x4 truss bottom chords. This will 100% draft stop the structure vertically to the attic. Foam will be nominally 4" thick. Then they will overblow with R30. Roof is normal construction with soffit vent and ridge vent.

Separately, we have replaced all of the nasty windows and doors and installed Tyvek (removed vinyl siding) and installed Hardy lap siding.

In the basement, we spray foamed the band board and overlapped the top of the concrete foundation by 1-2 inches to seal that off.

Not much more I can do at this point.

 

[yeldogt]

Location is everything for insulation performance, but I'll let you know if this Georgia redneck learns anything. I did not want spray foam. My current home build is going to be liquid-flashed Zip +3 sheathing on 2x6 framing @ 24" o.c. with 5.5" Rockwool batts and 5/8" sheetrock. Framing starts in two or three weeks. The insulated Zip (somewhat) breaks the thermal bridging of the studs. 24" o.c. means less studs to detract from the effective R value of the walls. The perimeter of the sheathing and under, between, and outside the sill and top plates will be sealed with acoustical sealant. It will get blower-door tested with leak remediation as necessary, so I expect that it will be a tight structure. Mechanical ventilation will be a conditioning energy recovery ventilator.

Every system has a plus and minus. With more Zip variations coming on it will be interesting to see the results ... the Zip impregnated sheathing products w/ outside barrier laminated to the panel eliminate many of the problem of OSB. It seems the Zip tape has been holding if it's installed correctly --- but, we don't have 30 years of testing. Personally -- all types of caulk worry me --- but, they have improved so much that the newest ones may be up to the task. Time will tell.

I started using spray foam because I did old buildings --- you don't have a way to stuff 5-6 inches of insulation anywhere. With maybe 4" on a roof -- typical on an old building with purlins ... what do you do? So you learn over time. I have also ripped apart many old buildings -- enough to see that you only want one air barrier and IMO -- it's better inside the sheathing so the building can dry to the outside. Buildings that dry don't rot.

I have done thermal imagining of some of my buildings -- I don't see huge amounts of thermal bridging ...maybe in really cold climates (hot) it's a bigger deal. I'm in the mid-atlantic. That's not to say it's not there.

I have also done HRV/ ERV's -- again ... with different systems out there IMO there is no fast rule. I don't like them for bathroom ventilation -- the boost was not enough and keeping it "on" only made the bathroom cold as it was pulling colder air from the rest of the house. I'm in the let's have a good Fantech fan system for each bathroom. Also -- with radon in my area I wanted a positive pressure in the house -- you can do it with an HRV/ERV -- but, its' going to be moving a lot of air. I found doing a simple controlled intake attached to the HVAC system was the answer --- since all the new VS systems can be set to have air moving around all the time anyway .... why not use it to move fresh air around and also dehumidify -- I use a whole house unit (that may indeed also not be needed today with the newest VS AC equipment)

Unfortunately, when building you have competing systems. The one that really kills me is the make up air requirement for the ranges ---- some done so poorly --- GBA had one with open vents under the stove ???? Super tight = more fresh air. Smaller w/ more people = more make up air. Nothing is perfect .... All are better better than a cave and fire pit

 

[yeldogt]

My house was built in 1987 and the attic insulation is for sh#t and I can see that none of the framed wall plates are sealed where drilled upward for penetrations (wires, plumbing vents, etc.). One can really feel the air flow thru some of the penetrations.

Insulation company will soon be un-blowing and purging the attic of all of the **** up there (hideous what prior owners did up there).

Once its purged, and all wiring sins identified and fixed, insulation contractor will be applying open cell spray foam to the top side of the ceiling drywall from outer stud wall to out stud wall and will bridge over the 2x4 truss bottom chords. This will 100% draft stop the structure vertically to the attic. Foam will be nominally 4" thick. Then they will overblow with R30. Roof is normal construction with soffit vent and ridge vent.

Separately, we have replaced all of the nasty windows and doors and installed Tyvek (removed vinyl siding) and installed Hardy lap siding.

In the basement, we spray foamed the band board and overlapped the top of the concrete foundation by 1-2 inches to seal that off.

Not much more I can do at this point.

Energy was really never cheap --- but, when you have a big heater pumping out hot air the stack effect is keeping the cold out -- all the holes are letting heat out. I had an uncle who lived to be almost 100 and he wrote down every oil delivery in a small book --- as well as the temp every Sunday ..... he did it for 50 years. I bought the house from the family to make a rental -- it was a cool craftsman. After it was rehabbed we figured out it used less than 40% of what it did before. Now some of that was the equipment ... but, most of it was just closing up the holes.

 

[jar944]

My house was built in 1987 and the attic insulation is for sh#t and I can see that none of the framed wall plates are sealed where drilled upward for penetrations (wires, plumbing vents, etc.). One can really feel the air flow thru some of the penetrations.

My house from 2007 isn't all that different, or more correctly isn't different at all. I keep meaning to get up in the attic and air seal everything and add more insulation. The amount of lady bugs and other insects behind the walls in my basement leads me to believe the sill and band joist are wide open as well.

 

[Firstram]

A coworker who used to own a carpet cleaning biz was chatting with our energy rater one day. The conversation evolved to include a situation he commonly found in tract homes, a black line in the carpet near exterior walls. As it turns out, carpet will filter the air that leaks in under your bottom plate!

 

[billconner]

Like insulation in attic - look for dark spots - dirt exiting through gaps, top plates, light fixtures, etc.

 

[beemerphile]

Buildings that dry don't rot.

^True dat...^

...but how much drying you need depends on how much water you have. A lots gets said about condensation on the cold face of of a wall and the need to dry it through vapor permeability. But if your WRB fails you may take in more water than you can dry, and the building rots. A lot of rot in spray-foamed wood framed buildings (and rust in metal framed buildings) is caused by failures in the water barrier that go undetected for long periods of time because it didn't leak to the inside and nobody knew. Also, if your air control layer is full of leaks, the condensation caused by airflow against the cold face can be two orders of magnitude higher (100 times or better) than the condensation of moisture in the static air within an air-sealed wall. Both of these can put more water into a wall than you can realistically dry out. You still get a wet rotten building, but the cause is not insufficient drying.

 

[reader2580]

My house was built in 1987 and the attic insulation is for sh#t and I can see that none of the framed wall plates are sealed were drilled upward for penetrations (wires, plumbing vents, etc.). One can really feel the air flow thru some of the penetrations.

Insulation company will soon be un-blowing and purging the attic of all of the **** up there (hideous what prior owners did up there).

Once its purged, and all wiring sins identified and fixed, insulation contractor will be applying open cell spray foam to the top side of the ceiling drywall from outer stud wall to out stud wall and will bridge over the 2x4 truss bottom chords. This will 100% draft stop the structure vertically to the attic. Foam will be nominally 4" thick. Then they will overblow with R30. Roof is normal construction with soffit vent and ridge vent.

Separately, we have replaced all of the nasty windows and doors and installed Tyvek (removed vinyl siding) and installed Hardy lap siding.

I did much the same thing in my house built in 1980. It cost me about $4 per square foot in 2014 to have the old attic insulation totally removed, spray foam applied to the back of the ceiling, and blown-in insulation put on top of the spray foam. I also replaced all windows and doors and had Smartside siding installed.

I have no idea how much the spray foam helped as it was done before I moved in. I can't compare the utilities either as I replaced baseboard electric heat with a gas furnace and central A/C. My utility cost is about 1/3 of what it was previously, but you can't compare the cost of straight electric heat with gas heat.

 

[mejhaha]

Getting back to OP’s questions; air sealing is very DIY. I would get a foam gun, not the self-dispensing kind. Between that, some Polyiso and XPS you can do a lot to stop the flow of air.

I am a little confused about your wall situation - I know your sheathing is short of your plates, but that communicates to your soffit? If so I would close this up and seal the joint.

I am not going to get into vapor barriers, but if you are talking about vapor that means you are talking about water (vapor), and a lot more water vapor can go through a hole in a wall where it doesn’t need to be than diffusing through a material - which is a case for air sealing.

 

[mike93lx]

Getting back to OP’s questions; air sealing is very DIY. I would get a foam gun, not the self-dispensing kind. Between that, some Polyiso and XPS you can do a lot to stop the flow of air.

I am a little confused about your wall situation - I know your sheathing is short of your plates, but that communicates to your soffit? If so I would close this up and seal the joint.

I am not going to get into vapor barriers, but if you are talking about vapor that means you are talking about water (vapor), and a lot more water vapor can go through a hole in a wall where it doesn’t need to be than diffusing through a material - which is a case for air sealing.

wow. how the heck did you hold off 4.5 years to make your first post?

 

[mejhaha]

First time I had something somewhat useful to say I guess!

 

[mike93lx]

First time I had something somewhat useful to say I guess!

Definitely not a criteria for posting!

 

[beemerphile]

"Blessed is the man who, having nothing to say, abstains from giving us wordy evidence of the fact.“ — George Eliot

 

[u3b3rg33k]

Air sealing is as important as whatever the R value -- maybe more. A small leak can move a lot of conditioned air .... and in a home it's one of the main items that determine comfort.

a 400CFM range hood is theoretically bringing in up to 1 ton of AC load in the summer. that's a lot if you have a 2 or 3 ton system.

Unfortunately, when building you have competing systems. The one that really kills me is the make up air requirement for the ranges ---- some done so poorly --- GBA had one with open vents under the stove ???? Super tight = more fresh air. Smaller w/ more people = more make up air. Nothing is perfect .... All are better better than a cave and fire pit

I've been looking for a good 30" range hood with decent capture efficiency. I have to run mine on full power if I use a front burner (NG) or it's almost useless. its got the fan back corner, and the front 4" do nothing but hold the lights. not a great design.