Leaving ceiling joists exposed.

[Bernie May]

I like this idea of putting some type of foam product between the joists and leaving them exposed in my garage. Any thoughts on this from some who have done it or thought about it.

[Lee Koepke]

I am considering the closed cell spray foam. It ranges from .35 - .60 / sq foot. I have alot of plumbing and electrical that would make either batt or stock foam difficult at best, and definately not a continuous coverage.

[Bernie May]

Ken-
Which product are you considering? Will you paint it? How thick are you planning on? When they say 605 bdft do they mean the final product will be that total volume? Any code issues in leaving it exposed?
-bernie

[NICK BARBOZA]

spray foam insulation is a great product. It offers a great insulation r factor and also if sprayed correctly produce a 100% vapor barrier. costs for a closed cell foam like isonene are in the neighborhood of $1 /sf/inch of thickness. one inch provides 3.6 r factor. there should be no code issues with leaving it exposed, but some types of foam are VERY flammable. so you can get a fire retardant spray for over them, but that is just more $$$$

cheers,
Nick

[Jim Becker]

The closed cell foam sprayed in our addition is not required to be covered in the attic where it is completely exposed. (Envelope...the attic is conditioned space) At R7 per inch, it's about the most efficient thing you can use and it also adds structural rigidity and a complete vapor barrier in one step. No air space is required between the foam and a roof deck, either, although some contractors still install baffles. The product is paintable (spraying obviously is the technique for that...). The most current versions also contain an additive to keep mold away, too.

[Joe Chritz]

My house and shop both have spray urethane foam.

It is the best you will find for insulation and about all you can do to leave it exposed. The spray room will have pink foam because I didn't spray it when doing the rest of the shop.

There are codes to leaving it exposed. A basement shop is most likely required to have a fire rated drywall ceiling, depending on the area.

Joe

[Eric Haycraft]

I just sprayed my basement walls with the help of my mother and it went pretty well. The foam costs like a dollar a foot as someone else mentioned. About half of what I saw on the market had a fire rating, but it was a few pennies more a square foot. All of the do it yourselfer foam that I found ranged from r6 to r7 per inch.

I don't know the specifics of doing a ceiling, so I can't comment on that. The foam websites should tell you of any issues involving that. I do know that it would be messier than what I did, so tyvek suits would be a good idea as well as covering everything with plastic while spraying.

The main benefit of foam is that you get a very good vapor barrier built in. When I did my walls, I did one inch of foam and the remainder of the cavity in fiberglass..airtight and not a budget breaker.

One thing to note is that this stuff breaks down under UV light, so they tell you to paint it with a UV blocking paint if it is going to be exposed.

[Gary Robertson]

if your shop is attached to the house the wall between the two has to have a 1 hour fire rate ubc code

[Bob Cooper]

Eric:

how does the cost of DIY vs. hiring someone cost?

[Phil Thien]

When I was younger, my father cut some strips of tempered hardboard about 4" or 5" wide and 96" long. He fastened these to the bottoms of the joists in the garage using roofing nails. This made each joist an upside down "T". He used the resulting ledge that was formed on each side to lay in some faced insulation. I was always surprised that the insultation didn't sag.

The beauty of doing this was that he could easily get back into the ceiling space if he wanted.

I can't duplicate that in my garage because my joists are 24" apart. He had a much nicer garage than I do.

[David G Baker]

Bob,
I have read discussions on the cost of doing the spray foam your self or hiring it done and the final thought was that the two prices are very close. If you spend some serious time researching foam installers for quality of product and quality of work you may come out far ahead using a pro over doing it yourself. Every time I get near one of those cans of spray foam for sealing around doors and windows I end up with a big mess. I can't begin to imagine the mess I would have with a big container of foam.

[Eric Haycraft]

I never got any estimates, so I can't say. It wouldn't surprise me if the DIY costs were similar to hiring it out. Since I was doing the work in my basement myself, it made sense to have total flexibility in when I could get the foam in.

And regarding David's comment, I found the 2 part spray foam to be simpler to work with than the can stuff. Having something setup almost instantaneously made it easier to deal with. That being said, it still makes a mess - and that mess would be 10 times worse if spraying overhead.

[Chris Mann]

Depending on the building department you may or may not be able to leave it exposed. We used demilec in our addition and left it exposed on the bottom of the roof deck in the attic. The manufacturer's ICC report implies this is acceptable, but the building official made us coat it with a fire retardant paint.

In a basement shop I'd still want to cover it with drywall to protect the foam from being punctured/ripped out.

[Joe Chritz]

Foam costs go up for hiring it out as the size decreases. The equipment is a pain to drag around from what I was told and most like to do a sizeable area when they do one.

DIY foam wasn't available when I did my house, at least not readily available that I knew about.

Joe

[Tommy Emmons]

Does anyone have any suggestions for cutting the heat gain into the attic? By that, I mean has anyone used foam on the bottom of the roof deck or some other method to reduce the heat gain that is radiated into the attic space? The less heat gain into the attic would result in a lower temperature in the attic and since heat gain to the interior of the living space is directly related to the temperature difference between the attic and the living space. I recently purchased an existing house and did not have the opportunity to do any work to reduce the heat gain through the roof deck. Thanks in advance.

[Lee Koepke]

Does anyone have any suggestions for cutting the heat gain into the attic? By that, I mean has anyone used foam on the bottom of the roof deck or some other method to reduce the heat gain that is radiated into the attic space? The less heat gain into the attic would result in a lower temperature in the attic and since heat gain to the interior of the living space is directly related to the temperature difference between the attic and the living space. I recently purchased an existing house and did not have the opportunity to do any work to reduce the heat gain through the roof deck. Thanks in advance.
you can insulate the top chord of the trusses or rafters. make darn sure you take into consideration air flow (ie dont block the ventilation paths from the eaves to ridge vent) air flow is important.

[Charles Wilson]

I just sprayed my basement walls with the help of my mother and it went pretty well. The foam costs like a dollar a foot as someone else mentioned. About half of what I saw on the market had a fire rating, but it was a few pennies more a square foot. All of the do it yourselfer foam that I found ranged from r6 to r7 per inch.

I don't know the specifics of doing a ceiling, so I can't comment on that. The foam websites should tell you of any issues involving that. I do know that it would be messier than what I did, so tyvek suits would be a good idea as well as covering everything with plastic while spraying.

The main benefit of foam is that you get a very good vapor barrier built in. When I did my walls, I did one inch of foam and the remainder of the cavity in fiberglass..airtight and not a budget breaker.

One thing to note is that this stuff breaks down under UV light, so they tell you to paint it with a UV blocking paint if it is going to be exposed.

Wow, sounds like you have a great mom! :)

Chuck

[Eric Haycraft]

They make an aluminum foil specifically for what you want to do. It can be applied on top of the existing insulation or used to create an air gap between the sheathing and the attic space.

[David G Baker]

Tommy,
Insulate the heck out of the ceiling joists and ventilate the heck out of the attic space is what I did in the ranch style house I once owned in Northern California. I installed a peak vent with a thermostat controlled fan, a whole house fan in the ceiling in the center of the house, three air/wind powered turbine vents evenly spaced on the North side of the roof and 10 inches of roll type fiberglass insulation.

[Jim Becker]

you can insulate the top chord of the trusses or rafters. make darn sure you take into consideration air flow (ie dont block the ventilation paths from the eaves to ridge vent) air flow is important.

With closed cell spray foam, the ventilation is no longer required as I mentioned in my previous post. However, some contractors still install baffles to maintain ventilation based on preference.


Does anyone have any suggestions for cutting the heat gain into the attic? By that, I mean has anyone used foam on the bottom of the roof deck or some other method to reduce the heat gain that is radiated into the attic space? The less heat gain into the attic would result in a lower temperature in the attic and since heat gain to the interior of the living space is directly related to the temperature difference between the attic and the living space.

This is what I was speaking about in my original post in this thread. In our new addition (2000 sq ft), the attic is considered conditioned space. Closed cell spray foam was done for a complete envelope. This means that the HVAC equipment "up there" is working in a conditioned environment and we can also safely store pretty much anything in the available space for the same. The contractor over-shot in the rafters, so we ended up with about an R50, rather than the R38 we contracted for. Gable walls are at R19+