Another Ceiling Insulation Discussion

[boneill1292]

Hi guys,

Long term lurker but first time poster. I am finally ready to start insulating my 34x24 detached garage with a hip roof. I have been googling non stop but figured I'd post my specific garage and see if anyone has any ideas.

Location: Iowa - Very humid and very cold
Ventilation: None - there is a fan on top that will patch if go spray foam route.
Primary Use: Gym and office, will heat and cool, but only on demand. Not full time. Will not be storing any vehicles.
Considerations: Wiring is already all over the garage. I wont be redoing it. But it makes the **** from wall to ceiling kind of a pain.

I am not against doing spray foam (cant figure out if open cell is ok), but the concern is that my garage is under two very old maple trees. So it's not out of the question that some day a branch could damage a shingle without me knowing. I am a proactive homeowner, but if water was leaking beneath the shingle I would have no way to know.

I am willing to install the soffit vents and ridge vent myself and building a ceiling out of plywood or steel. But after pricing out all those materials it's not too far away from the spray foam install. Also - the old fart farmer before me has wires run all over the place. Will have to get creative with my notches to get it semi flat.

Plan to live in this house for a very long time. Will not have the funds to replace rotting framing if something were to sneak behind the shingles and rot the wood if I went closed cell. Willing to take the risk but would like to hear from the experts.

Thanks a lot!

 

[Dragfluid]

Put in a ceiling and blow in a bunch of cellulose.

 

[bdbecker]

First of all, welcome to GJ neighbor! It's always good to see another Iowan on the forum.

Regarding your question, what sort of R-value are you having quoted on the spray foam? Living where we do, the more insulation in the ceiling, the better - especially if you plan on conditioning the space. If you only are intending to fill the cavity to be flush with boards, depending on if those are 2x4's or 2x6's, it might be tough to get much more than R-20 or R-30 with closed cell spray foam.

I ultimately chose to sheet my ceiling and use R-38 batts when I was weighing out my options a few years ago. It was a big more work to install soffit vents and sheet the ceiling, but I'm happy with the results. Eventually I'd like to install a mini-split, at which time, I'll likely consider adding more insulation.

One advantage of sheeting the ceiling is that it reduces the volume of air that you need to condition, which will save you money in the long run. Another advantage is that it'll help make the space feel more finished by not having to look at all the roof structure. Open rafters can look cool in certain builds, but at the same time, can look a bit cluttered. They are also great spots for dust to collect.

 

[billconner]

I'm with the ceiling and cellulose, and vent attic. Looks like you have a start towards high vents. And just gutters in decline or do soffits and fascia need work?

Dont forget that with foam, you need a ceiling or some covering for foam's flammability so figure that into overall cost.

 

[charbar]

If it were me I would also do a ceiling and blow in insulation. Definitely vent the attic portion.

Since you are in Iowa you should have a Menards close. Right now they are doing their 11% off....sometimes they run pretty good deals on their insulation ontop of that. You can rent from them to even blow it in yourself. Wouldn't be a bad job at all on a garage off your size.

 

[Dragfluid]

Before you put the ceiling in, add a box to hand a ceiling fan on. It makes a difference!
In fact, with 24x34, two fans would be prudent!

 

[CraigStu]

Agree on ceiling and blown in. You would need to verify but I 'think' steel liner panel can span between your ceiling joists by itself. This would be relatively easy and quick to do. Because of your concerns I am not a fan of spray foam. I guess it can be done but, if you need to get into a wall to do a repair or run an extra wire, pulling out rockwool or fiberglass is a 20 second job. Removing foam would be a bear. Also think about venting the attic area. Common is ridge vent and soffets. But it would be a lot easier to add another of the roof vents that is already there. And do you want to vent the attic in the winter? Might be better to cover over those vents in cold weather.

 

[billconner]

Might be better to cover over those vents in cold weather.

My take is not, that winter is when you're most likely to get condensation of warm moist air bypassing ceiling. The pressure is greatest in winter - warm bouyant air.

I do agree you can get by with other than ridge vents.

Don't underestimate the importance of the right balance - like 60% low intake and 40% high discharge. Too much high is going to **** more of your heated air out.

 

[Sumboodie]

Put in a ceiling and blow in a bunch of cellulose.

Yes, but fiberglass

 

[hop up]

I say spray foam 1.5 of close cell on the exterior surfaces and then 2.5 or better on top of that. It will not only insulates but will seal and bond the building. It’s a bit pricey but save on energy costs . I have a 25x36 with 2x6 walls and have a cheap 50 dollar electric heater that heats my shop excellently

 

[Dragfluid]

Yes, but fiberglass

Cellulose is more cost effective and better fire retardation!

 

[Sumboodie]

Cellulose is more cost effective and better fire retardation!

You sure on fire?
For a while my insurance wouldn't cover cellulose insulation.

My old house was done in fiberglass, if cellulose was cheaper, they'd definitely have used that if they could. Builder was tighter that 2 coats of paint... and it was the "model home".

Looking it up, seems like it's all over about which is better, so I'm not sure!

My understanding was it's much heavier and has less r value due to compaction over time.
But some articles say it's a way better insulator due to do air flow.

I know it absorbs moisture (leaks, humidity which makes it really heavy.
I've shoveled old stuff out and it was almost as bad as shoveling gravel with how heavy and packed it'd gotten. Fiberglass doesn't do that.

I didn't know cellulose was still sold even, haven't seen it used in 25+ years.

Pretty sure I'm using fiberglass on my.place.
Had a roof repair last week which meant opening a section and found there's barely r13 in the attic. Just 4" batt laid out.. and not even laid out well.

Probably going to wait until winter,much rather be up there when it's 20* outside vs 80... and like 800* in the attic.

 

[Dragfluid]

"I didn't know cellulose was still sold even, haven't seen it used in 25+ years."
Oh my, you've got to be kidding?!
Yes, cellulose if very much alive and well! Last spring had a **** ton blown in the house attic. And that fall, another 11" into the shop attic. I'm a very strong proponent of insulation, and cellulose in particular. Look at my old build thread in the link below.
As far as the fire thing, yes, there's been studies and tests. When I was building the old shed, I did one hell of a lot of research on insulation. That's why I was able to heat that 42 x 72 x 14 shed with an 85,000 BTU furnace to 75F easily. (and not have it running constantly, either) There's some videos about fire retardation with different types of insulation in the walls. From bad to worse, it was none, fiberglass, cellulose. You can search, but I'll see if I can find them too.

 

[bdbecker]

I'm a

...I have a 25x36 with 2x6 walls and have a cheap 50 dollar electric heater that heats my shop excellently

...That's why I was able to heat that 42 x 72 x 14 shed with an 85,000 BTU furnace to 75F easily...

Insulation is truly worth the investment... I run a cheap oil filled radiant heater in my 24x24 during the winter. During a normal winter temps (15-20F), the medium setting keeps the space around 45F, which is plenty warm for me wearing a hat and a hoodie or flannel. I'm out there nearly every day for an hour or two after work, so I don't mind running it all the time to keep things comfortable (and to keep things from freezing). If I intend to spend the whole day out there, or it's really cold, I'll fire up the kerosene heater for awhile.