Was considering spray foaming my attic. Either closed or open cell.... So... do I do the attic floor and not the roof rafters ? Just the roof rafters and gable ends? Or both ?

My ac air handler unit is in the attic. The foam company said I should do foam on the roof rafters. Said it would help the unit more and keep the home warm. Everything I read is floor! Anyone?

Google says attic floor!

I'm no expert,...but common sense tells me that if you keep the heat below the attic floor it won't get the opportunity to go out the roof.

Just the floor. Keep a cold roof. You should look at blown in cellulose.

Make sure to baffle between the rafters at the side wall to maintain soffit ventilation.

The squirrels prefer the pink cotton candy. So, they'll be disappointed.

Expect reprisals

I had my whole house done in spray foam. Upon recommendation of my builder, we did open cell on the walls and closed cell on the roof. My electric bills average about $125/month, which in Texas, is exceptional. My builder thinks the low energy consumption is from being air tight as much as from the R value. Could be. We have to crack a window for the wood burning stove to get enough of a draw until it’s good and hot.

John

So you did not do the attic floor?

Rodents love spray foam. I’ve opened walls that looked like the rodent version of an ant farm—store food here, defecate and dispose of the dead here, sleep and reproduce here, play and fidget here, expand tunnel network here, here, and here...

I loath Icynene. My experience is in the north where we have four extreme and distinct seasons.

Google cold roof.

You live in the north. What they do in TX has limited relevance.

Subterranean Termites love spray foam, in crawspaces in the southeast.

They get behind it and come right up.

I used to cancel control warranties when people sprayed that chit on their foundations.

The ones that really stumped me were the ones sprayed that liquid paper pulp soul crap. Mmmm, termite candy.

We super insulated the whole house. First, we installed a silver/Mylar infrared reflective film on the rafters. Then, we added to the blown-in insulation. Also added a solar-powered attic fan. Finally, we installed water-based non-expanding foam between the outer brick walls and the inner sheet rock in addition to the original insulation there.

HUGE difference. In the summer, when it hits 100° degrees, the A/C unit doesn't even kick on until late afternoon. The reflective film keeps hot air from accumulating in the attic - it doesn't get above ambient temp up there, even in summer. The foamed walls keep the heat from the bricks from radiating inside, and make the house both airtight and almost soundproof. A west-facing interior wall that always got hot to the touch now stays cool.

We could not be happier.

Kingston I've never seen the foam in the attics

See it walls down here and foundation.

Most still go with batts in the ceiling joists.

Borate

That might work in a dry climate. In one with extreme temperature, and humidity swings, it’ll rot out your roof sheathing. In the Northeast and Midwest you need a cold roof that allows air to circulate around the roof structure. It’s called a cold roof.

Yup, up here batts between the joists, blown insulation on top, continuous peak roof vents, and vented soffits.

Is that Cellulose insulation???

I thought attic insulation needed to breathe? Fiberglass rolls, no paper unless you slash the paper.

He talking about in a crawl space with ground contact or near ground contact. It would be a misapplication. Poor application and misapplication are common with insulation contractors. They typically have what is some of the least sophisticated labor in the trades.

Either way, quality cellulose insulation is treated with borates, which destroys termites ability to digest anything and they die.

None of this is an issue in your attic.

Warm air is full of moisture, when warm air hits a cold surface you get condensation. Excess moisture results in mold and fungal activation. Mold and fungal activation lead to health issues and rots wood.

I've been out of the wood destroying organism biz for about 20 yrs. Seems it was a new thing at the time here then, it might not have been pre treated at that time.

Good to know if it is now.

The crap I remember looked like a mix of glue and a dump truck load of shredded financial reports. Sprayed onto a crawlspace wall. lol

As to advice: step on the rafters, not between them.

+1

Vapor barrier facing heated/cooled area aka living space..

That's how I always did it anyway...

Looks like a new day and a new way, don't know if I totally get it but it's probably the way to go with spray foam

I have a patent advancing building envelope design.

This. The soffitt insulation is very important. You do want a cold roof. In cold climates, they won't approve a hot roof.
Cellulose not only works it has an additional product like borax, and is more fire resistant. Nothing wrong with it at all.

When I get ready for it, I'm blowing cellulose (shredded paper) insulation in my attic. It's treated to make it fire resistant and with boric acid for bugs.

On wood framed structures I’m a fan of conventional schemes.

Spray foam is taking off here in the Midwest. Great reviews.

It’s not which one is better. Google conditioned attic

In the South, ceiling.

In the North, rafter if you’re doing a conditioned attic.

I don't know much about the foam, but I do know a good bit about conventional in areas where it really matters.

I am gonna have to watch some of these newer homes getting all foam or "air tight" insulation jobs.
I see them going up but never paid much attention.

I do know I can tell a lot about a homes insulation when there is snow and or ice on the roof.
It's kinda a tell tell sign of just how well the insulation job went, especially soffit and baffle work.

I can see what they are after in the illustration but not so sure I want to heat and cool all that attic space to achieve it.

What is your advanced envelope design?????

What kind of roofing do you have.
If you have asphalt/fiberglass shingles, and if you insulate the roof, between the rafters, that's great in winter. That will help with you heat bills. Not as much as insulating the ceiling, but it will help.
Where you will get bit in the ass is in the summer, which in Texas is 9 months long. The ceiling insulation will trap the heat that comes through the shingles, and the shingles will overheat every sunny day.

And your 30 year shingles will last 12 years. I know what I am talking about.

If you have a metal roof it is Macht Nichts.

My friends brother just had his new home sprayed with the foam. The ac/heat contractor said he needed x size unit for the structure and installed the units but didn't come back for startup The owner contacted another ac/heat contractor to come for startup and this contractor, after looking at the system, wouldn't touch it. Second contractor said it was entirely wrong for the spray foam insulation. The contractor said the units were too big with the foam Insulation, IIRC. He contacted several more contractors to make sure he wasn't being steered wrong, and wound up spending 17K changing out the ac/heat units. He lawyered up and is after the first contractor.

The only part of my house that has an attic is over the garage. We didn’t foam the attic floor there, just the walls and roof of the entire house. The rest of the house has no attic except a little under eave storage. The great room has a cathedral ceiling and there is a loft over the bedrooms, so no attic floor to insulate.

John

As a sideline to our contracting business we've been spraying primarily closed cell (2 Lb.) foam for 15 years. If you have air handling equipment in the attic spray the rafters so it's not working in extreme tempatures. I've heard the shingle warranty thing but never talked to a roofer that experienced it firsthand. Houses that are sprayed from the ground up are extremely tight and usually require some forced ventilation, something their hvac contractor should take into account. Sprayed an attic once, residents started complaining of headaches , turns out they had a defective furnace, been causing health problems for years. Did a little work for the government sealing mine and ventilation shafts, used it once to support a 2 ft thick concrete slab, 60 feet across, amazing stuff.

Not following you here, with "air handling equipment" are you referring to the actual duct work or compressor units?



Way back when, with homes that were considered "air tight" we use to put bathroom fans on timers so the cycled multiple times a day for various intervals of time. We also installed vents much like dryer vents for air intake in selected locations in a home.

What is done today to achieve fresh air exchange?

That’s another thing- I’ve read a few complaints of the foam giving off toxins...? Smelling?

Compressors are outside, the ductwork and blower are indoors. Most air handlers (blower) have some type of auxiliary heat available, gas, water, or electric. Having the handler in conditioned space allows for less energy loss. If your 72 degree air must travel through ducts in a 130 degree attic it's gonna take more energy to keep cool.
The only odors I've ever experienced have been just when the foam was sprayed, usually gone within the hour if you open the windows, not near s bad as most paints. The spray is a reaction between 2 components, is heated at the pump and mixes at the spray gun nozzle.
Good question about the controlled ventilation, last full house we did had a duct running outside to the handler. I'm sure it's a controlled fresh air intake just not sure how it's controlled. I'll try to ask one of the hvac guys tomorrow .

Had a area professionally spray foamed, all concrete walls and ceiling. There were exposed I beams that supported the concrete ceiling that had been sweating. Due to the area was intended to be used to grow plants was the reason for getting it all foamed.

A few months into the grow show and had noticed some small areas of the I beams that were still exposed and rusting fast. Picked up a couple of cans of spray foam, whatever type it is on the shelf at Home Depot.
Emptied them both in the very well ventilated room (25x35), came back the next day to find an all but total meltdown of 150 plants. Every plant was wilted and appeared to be dying. Took a couple days for them to completely snap out of it and perk back up, these were pretty mature plants.

Yeah, the stuff off gases something that isn't so great. Again this room was ventilated very well with a few horse power of inlet and outlet ventilation fans running at the time.

Here in Newyorkistan,any new build is required to have "make-up air",we use a fan induced system tied into the ductwork,an HRV unit or with bath fans.
Houses are so tight,you have to bring in 0 degree air in winter,or 95 degree air in summer and condition it.