Spray foam Questions.

[sixty4]

I own a house built in 1997. I am thinking of having a company do spray foam on the underside between roof rafters and side walls in attic. I have no insulation currently but do have soffit vents and at the ridge have a roof ridge vent.
What happens to the soffit vents and ridge vent when they spray foam, obviously don't want foam out the vents or roof (lol).

Also while reading up on this people have mentioned because making a house tighter messes up the radon system somehow ?

Thanks for any help or suggestions with this!

 

[PCustoms]

I'm not quite following where you are going to be spraying. You have 0 insulation there now?

Typically the soffit vents get a baffle/channel stapled in to keep the airflow up to beyond the height of insulation.

If you are foaming the underside of the roof, then this attic is now conditioned space, and will need to be sealed up.

The concern regarding radon is actually about making the house tonight in general. If too tight you need an air exchange to bring in fresh air.

Also making the house tighter could possibly let anuly radon already in the home possibly build up to da negros levels. You would have to add a sub slab fan.

 

[Fly YX]

You will still need air flow in the Attic. For the gable vents they will put Ridgid extensions on the attic side of the roof decking. Do you know what kind of spray foam they will put on there's open cell and closed cell? If you have a leak on the closed cell the water will not absorb into the foam and can get stuck between the roof decking and the spray foam causing the wood to rot. On open cell the water will go straight through. I did the spray foam in my house many years ago I don't know how much of it has changed since then.

 

[Fly YX]

On the radon system assuming you have a basement you will have to have an air exchange down there too especially if you have gas appliances down there. They make ventilators just for basements to bring in fresh air.

 

[Lelandwelds]

You will still need air flow in the Attic.

No, you do not.


Try thinking of your roof as your fifth wall and go read some articles.
https://buildingscience.com/documents/insights/bsi-001-the-perfect-wall

Figure out where you live and study "mixed humid construction" or whatever is appropriate.

My attic is conditioned space. The roof deck is foamed. I worked hard at it and my house leaks enough an air exchanger isnt needed. Remember, the internet is full of idiots and half truths.

 

[23ford]

someone makes a kit you can spray this your self.....

 

[PCustoms]

someone makes a kit you can spray this your self.....

Tigerfoam and foam it green.

Pro contractor came in a price lower then the materials for me, I did about 3500 bd ft

 

[DC73]

What happens to the soffit vents and ridge vent when they spray foam, obviously don't want foam out the vents or roof (lol).

It's easy enough to cover the vents from inside the attic before spray foaming. Your spray foam company may do this or they'll have recommendations on how best to cover the vents.

DC

 

[DC73]

No, you do not.


Try thinking of your roof as your fifth wall and go read some articles.
https://buildingscience.com/documents/insights/bsi-001-the-perfect-wall

Figure out where you live and study "mixed humid construction" or whatever is appropriate.

My attic is conditioned space. The roof deck is foamed. I worked hard at it and my house leaks enough an air exchanger isnt needed. Remember, the internet is full of idiots and half truths.

Agreed.

However, there was some talk awhile back among building scientists that conditioned attics in some climates might be best maintained by having a small amount of conditioned air available to the space. I don't know how those discussions came out and whether or not they reached a definitive conclusion. I quit following those websites when I made the decision to buy instead of build.

DC

 

[Jeepster04]

While I've not read up on it, Ive always been against spraying the underside of your rafters. Its just a waste to heat/cool an attic when its not needed. More so when your units are not sized to do so, its just a waste IMHO.

 

[chaosracing]

While I've not read up on it, Ive always been against spraying the underside of your rafters. Its just a waste to heat/cool an attic when its not needed. More so when your units are not sized to do so, its just a waste IMHO.

Actually it makes it a better environment for HVAC systems. Think about this, most AC/Heat ducts have only R-6 insulation on them, not very good in the summer when temps get near 150 degrees in attic space. Same for heating in the winter time. Thats helps the equipment run more efficiently. That has even been said on This Old House that its better to put this equipment in conditioned spaces. Meaning insulated, you do not have to heat or cool those spaces though.

I plan on doing the same thing some day in my attic. There are two ways to do this.
#1 Close off all vents, block off the space at the rafters and walls so you dont get spray in the soffit.
#2 Run baffles from the soffit all the way to the ridge vent, then seal both ends so spray foam does not get in. You are allowing air to flow under the roof while insulating the space.

 

[Ryan Wilke]

Fellas,
Although it wouldn't do much for winter monts, but if the OP adds insulation to his attic, wouldn't he benefit from a gable exhaust fan with an inlet gable vent at the other side of the attic? I've seen some nice thermostatically-controlled gable fans that will keep the attic temps cooler in summer....?

Ryan

 

[chaosracing]

Fellas,
Although it wouldn't do much for winter monts, but if the OP adds insulation to his attic, wouldn't he benefit from a gable exhaust fan with an inlet gable vent at the other side of the attic? I've seen some nice thermostatically-controlled gable fans that will keep the attic temps cooler in summer....?

Ryan

Not really. I have been in attics with systems like that, no change really except in your electric bill. If you want a fan option, whole house fans would be the way to go, but thats only if you do not have AC or like to have your windows open.

 

[Greenlawnracing]

I know nothing about anything, which is why I ask stupid questions on this forum every day.

But my house came with spray foam, and it is freaking awesome. Utility bills are significantly less than in the past.

 

[tomshep]

OP-what state are you in? I can't tell if you are trying to keep heat in or heat out of the attic.

I am in TX. All I can say is adding ridge vents, soffit vents and a ton of "turtle" vents has helped my attic stay much cooler. Best part is I don't have a attic fan using electricity to try and save me money.

Tom

 

[Fly YX]

No, you do not.


Try thinking of your roof as your fifth wall and go read some articles.
https://buildingscience.com/documents/insights/bsi-001-the-perfect-wall

Figure out where you live and study "mixed humid construction" or whatever is appropriate.

My attic is conditioned space. The roof deck is foamed. I worked hard at it and my house leaks enough an air exchanger isnt needed. Remember, the internet is full of idiots and half truths.

If you have a traditional stick-built structure with asphalt shingles if your attic is not ventilated your roof will not last as long. I do not need some document to tell me this. It's a fact. If you live in a Northern climate during the winter if you don't have good insulation between let's say your conditioned area and the attic the moisture content in the Attic will be higher and you may see condensation or Frost on nails that are on the roof decking poking out in the Attic and you may get ice dams.

 

[skippydoo]

A builder friend of mine spray foamed his whole attic and made it basically an Igloo. About 10 years later, no issues and he loves it. The attic is never more than 10 degrees hotter than the warmest room in his house and the home has central air. The attoc is completely closed off.

 

[sixty4]

OP-what state are you in? I can't tell if you are trying to keep heat in or heat out of the attic.

I am in TX. All I can say is adding ridge vents, soffit vents and a ton of "turtle" vents has helped my attic stay much cooler. Best part is I don't have a attic fan using electricity to try and save me money.

Tom

I am in CT trying to lower our heating bill. After it snows our house has a fast rate of snow melting off the roof, leading me to believe we are losing a ton of heat in winter. Also would think it help with the ac as well.

 

[PCustoms]

I am in CT trying to lower our heating bill. After it snows our house has a fast rate of snow melting off the roof, leading me to believe we are losing a ton of heat in winter. Also would think it help with the ac as well.

Yeah, your current insulation is not adequate.

Can you sketch your attic?

Is there any insulation on the "floor" of the attic?

Is there any HVAC equipment, so rage etc. In the attic?

Having Ridge and sof fit venting your attic is unconditioned space and shoukd have a vapor barrier and insulation seperating the living space below.

If you spray the underside of the roof deck without sealing it all up it gets you almost nothing. If you seal up the venting the attic is now considered conditioned, and you will have to watch for adequate airflow.

Cheapest bet may be some new blown in on the floor.

 

[sixty4]

Yeah, your current insulation is not adequate.

Can you sketch your attic?

Is there any insulation on the "floor" of the attic?
Yes 2x8's insulated covered with 3/4 plywood through out

Is there any HVAC equipment, so rage etc. In the attic?
Yes all second floor duct work runs up there covered in R8 insulation

Having Ridge and sof fit venting your attic is unconditioned space and shoukd have a vapor barrier and insulation seperating the living space below.
No vapor barrier of any kind that I can tell, I am thinking the kraft side is down touching the sheetrock?


If you spray the underside of the roof deck without sealing it all up it gets you almost nothing. If you seal up the venting the attic is now considered conditioned, and you will have to watch for adequate airflow.
I think you are spot on something I do have a concern about

Cheapest bet may be some new blown in on the floor.

Not sure I have any area left as the joists are filled and covered with ply wood for a walking and runs throughout

Thanks for any reply, I am stumped. I will have someone come in to spray, but want to be informed as much as I can be.

 

[PCustoms]

Not sure I have any area left as the joists are filled and covered with ply wood for a walking and runs throughout

Thanks for any reply, I am stumped. I will have someone come in to spray, but want to be informed as much as I can be.

Well I pretty much layed out your two options, insulate the floor, or spray the roof deck and seal it all up. Cheapast is still going to be bulking up your insulation that is there.

For reference, I have 100 sqft of attic space, no HVAC ducts. 1 passive gable vent, vented soffit and 10x50 vented ceilling above porch. As far as exhaust, 1 power gable vent, 2 powered exhausts in the roof. I had r13 last winter, kraft faced towards interior. Ripped it all out, added baffles to the soffit vent and a barrier wall to the porch area. Sprayed in 2" closed cell to get everything air sealed and then blew in 18" cellulose to add bulk insulation. Toasty warm in here now and redused air ingress into the conditioned space 25%

 

[DC73]

If you have a traditional stick-built structure with asphalt shingles if your attic is not ventilated your roof will not last as long. I do not need some document to tell me this.

The discussion wasn't about a traditional attic. It was about converting a traditional attic to an "unvented" attic by spray foaming under the roof deck. A perfectly acceptable approach. Not all attics need to be vented. In some locales subject to forest fires, vented attics are forbidden.

DC

 

[TractorJeff]

sixty4
What kind of access do you have to your Attic?
I ask because in my house there was a ceiling fold up type of stairs.
I put thermometers in the hall wall to actually validate that all the heat was going up the attic stairs and out!
I built a blue foam box that gasket seals to the floor around the stairs.
You access the attic just tip this out of your way, do what you need to do, then close it before you put the stairs up.
Biggest way I could tell it works is snow no longer melts off the roof like it did the first year we moved here!

 

[sixty4]

sixty4
What kind of access do you have to your Attic?
I ask because in my house there was a ceiling fold up type of stairs.
I put thermometers in the hall wall to actually validate that all the heat was going up the attic stairs and out!
I built a blue foam box that gasket seals to the floor around the stairs.
You access the attic just tip this out of your way, do what you need to do, then close it before you put the stairs up.
Biggest way I could tell it works is snow no longer melts off the roof like it did the first year we moved here!

I have the same type of pull down attic stairs. Good tip on making the blue foam box! That's my problem when it snows as well, our house is one of the first houses to have a clear roof after some snow. That's what got me thinking end of last year on how much heat we may be losing.