How should I insulate my shed?

56912 Views 19 Replies 4 Participants Last post by searcherrr, Jun 21, 2010

kbizzle

Discussion Starter · Jul 10, 2009

2

Hi everyone,

I'm new here and just wanted to say that I've already learned so much from researching this site. It's a great resource.

So, I'm having a 16' x 16' shed built in the backyard. I plan to use it as a workspace / project studio / retreat and I want to finish it with insulation and drywall. I plan on using a 12,000 BTU portable A/C in the summer and some sort of portable garage heater in the winter. I'm in Durham, NC so the summers are hot and winters can be quite cold. The shed will be a mostly shady spot because we have a nice canopy of trees in the backyard. I thought insulating the shed would be relatively simple but after almost a week of research I'm puzzled.

I plan on using R-13 fiberglass batts in the walls and finish them with drywall. The ceiling / roof is where I'm running into problems. The roof is framed with 2 x 6 at 24" on center. There's a ridge vent that runs almost the full length of the shed and a gable vent on each side. I've included some photos here so you can see exactly how it's setup. The photos are of a 12 x 16 demo shed on the lot (mine is just now being built).

The contractor says not to staple batts between the rafters because it will most likely hold moisture up against the roof decking. That makes sense to me. They suggested rigid foam board or possible some foil backed bubble insulation. Rigid foam board insulation kind of pricey and I'm not sure it's the best option.

Here are the photos and any suggestions would be most appreciated.

Thanks!

See less See more

1 - 20 of 20 Posts

kbizzle

Discussion Starter · #2 · Jul 10, 2009

Forgot to mention that I'm concerned that if I just insulate the roof with foam board or a product like Prodex Total Insulation (http://www.insulation4less.com/prodex_Ffmf.asp) that the ridge vent and gable vents will allow so much air to escape that it won't be effective.

I'm considering finishing the ceiling by attaching horizontal 2x4's (maybe 2x6s) to the rafters at 24" on center to create a frame for hanging drywalll to the ceiling. I could then use R-19 fiberglass batts or Prodex in the ceiling and then there would be a continous air space above the insulation so the ridge and gable vents could work as intended. There are no soffit vents in the eaves. The ceiling would form a seal between the shed workspace and the shed attic. Does that make sense?

The outside walls are 8' but if I drop the ceiling where the framing meets the rafters that's only about a 7' 8" headspace. I was thinking of hanging the ceiling a little higher on the rafters to form at least an 8' ceiling. I don't plan on using the attic for storage so I don't think that would cause any structural concerns.

See less See more

Scuba_Dave

· #3 · Jul 10, 2009

2

Having a shed built....or already built?
I prefer a bran style shed - lots of extra storage room up top

You use a rafter vent against the plywood for ventilation
Then insulation
With 2x6's you could still use R13

See less See more

kbizzle

Discussion Starter · #4 · Jul 10, 2009

Thanks, Dave. I've seen those rafter vents before but would that require cutting holes into the eaves for them to function properly? Or do the vents just keep the batts from pressing up against the OSB roof plywood?

Yeah, I like barn roofs for that exact reason too but had to compromise because my wife hates the way they look (???).

Scuba_Dave

· #5 · Jul 10, 2009

They keep the batts from pushing up against the roof decking
Heat will rise & cooler air will sink
It would work better with soffit vents

Have you thought about putting joists across for a flat roof?
That would reduce the space that you would need to heat/cool
It would eliminate the need for rafter vents & allow ventilation up there w/the gable vents/ridge vent

kbizzle

Discussion Starter · #6 · Jul 10, 2009

Dave,

Yes, that's what I was trying to explain in my second post. I think about raising the joists up about 8" to 12" to increase the headspace. There would be an angle on each side of the ceiling close to the wall. That may be the best way to go.

Scuba_Dave

· #7 · Jul 10, 2009 (Edited)

Ah, I missed that - must have been typing up my post - slow :laughing:

Yes - I'd run 2x6's straight across even with the rafters
You should be able to sit them on the wall if you angle cut each end
But to go 16' you would need to go to 16" OC
-even that would be pushing the span allowed
2x8 would be better - angle cut each end

kbizzle

Discussion Starter · #8 · Jul 10, 2009

2

dave,

thanks again for the info. so, here are a couple of updated illustrations of what i'd like to accomplish. ideally, i want to create a raised ceiling for more head room. check out the illustration with the red beams.

in the raised ceiling scenario, i believe the span would only be about 10'. the only weight these joists would bear would be the weight of the 1/2" drywall. i would not be using the space for storage of other items in the attic.

if there's no good way to accomplish that then i could go with the scenario the blue joists illustration. you think 2 x 8 at 16" on center would be necessary there though, right?

thanks again for all your help so far!

kb

See less See more

Scuba_Dave

· #9 · Jul 10, 2009

2x6's 24" OC will span 10'
They will act as rafter ties too = keeping the walls together
This is the span calc I use
You enter the wood species, size, use (joist, rafter etc) & calc & it tells you the distance you can span

http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

Up here we have to worry a lot about snow load
I actually re-used 2x10's as rafters for my 10x10 cabana addition
They came off my house whan I dormered the back
With snow I stick to 16" OC here

kbizzle

Discussion Starter · #10 · Jul 10, 2009

dave,

thanks for the link and for all the super-quick replies. much appreciated!

kevin

Scuba_Dave

· #11 · Jul 10, 2009

Your welcome
I just happened to come down off the roof (new roof on addition)
Going back up now :thumbsup:

beerdog

· #12 · Jul 11, 2009

Don't you have to have open eave vents or some type of equal amount of intake with ridge venting? it could actually work in reverse from what I have been told and read a bazzilion times in the roofing section. Then again it is a shed.

beerdog

· #13 · Jul 11, 2009

Also, the roofers will say that ridge venting and gable venting in the same roof is a big no-no. both are considered exhaust venting and there should only be 1 type of exhaust vent. The visitors of the roofing section have been lectured a million times by "Ed the roofer".

By the way, great looking shed. Wish it were mine.

Scuba_Dave

· #14 · Jul 11, 2009

That's actually the 1st shed I've seen a ridge vent installed
If it was a house I might change it
But as someone pointed out...heat will rise
So it may not be the perfecxt setup - but it will work

Just make sure those gables have very good screening to keep wasps/bees out
In my MIL's house they came loose & she had quite a few nests

kbizzle

Discussion Starter · #15 · Jul 13, 2009

thanks beerdog and dave. my shed is actually just being built this week. i may take your advice and request that the ridge vent not be installed since there are no soffit vents in this design.

dave, great idea about doubling up the screening on each gable vent. i can't stand bees and wasps! :thumbsup:

kbizzle

Discussion Starter · #16 · Jul 15, 2009

2

Best way to fasten the ceiling joists

hey folks,

so if i raise the ceiling joists up one foot the raised ceiling height will be 8' 6" which would be perfect.

here is my drawing:

i'm a newbie at this stuff so please bear with me here.

the span where the bottom of the rafter meets the bottom of the joist (red beams) is going to be right at 12 feet and it's going to fall at about 1 to 1.5 feet up the rafter board from where the rafter meets the top of the framing. the roof pitch is 5:12. i'm planning on using 2 x 8's for the ceiling joists at 24" on center. the way i understand it, if the joist is attached to the rafter and it is in the bottom third of the height of the top of the roof to where it meets the rafter, then it is considered a rafter tie and could help form a stronger roof system. the collar ties are every 48" and they're staying! i will not be using what's left as attic space for any type of storage. i just want to hang sheetrock for a ceiling and add insulation in that space.

i have a few more questions so here goes:

1) do you think i should sister the rafter with another 2 x 6 in this 2 foot region (from the frame up past where the rafter meets the ceiling joist) to help brace the rafter against the new vertical load of a 2x8 plus 1/2" sheetrock? i'm not sure how much this would help since the joists will be pretty close to the base of rafter and framing.

2) would it be necessary or a good idea to place a strongback or ribband down the center of the joist span to prevent bowing and swaying?

3) how should i actually attach the joists to the rafters? nails? screws? or 1/2" 4" long hex bolts?

4) i've spent a few days searching the web for examples of what i'm doing and i've found others who have discussed doing the same but haven't seen any finished photos or even summaries of how it turned out. *sigh* would you consult a structural engineer?

thanks everyone - i'm probably overthinking this but i really want to have a solid plan before i begin.

See less See more

Scuba_Dave

· #17 · Jul 15, 2009

If the shed isn't built then 9' walls might be a better/easier idea
I did 9' walls in my sunroom - big difference
And then you can just put ceiling joists straight across

kbizzle

Discussion Starter · #18 · Jul 15, 2009

yes, dave, i think you're right. 9' walls would be the easiest but it's not really possible and not worth the expense at this point. i'm just going to run 2x8's at 16 o.c. straight across the top plate of the framing. that'll give me a solid 7' 7" or 7' 8" ceiling. with recessed lighting that should be sufficient for a nice conditioned workspace and enough attic space for insulation.

thanks for setting me straight with this issue. i needed some direction there.

Scuba_Dave

· #19 · Jul 15, 2009

Another thought
If they use 8' studs & have a bottom & top plate that equals 8' 3"
Every little bit helps

searcherrr

· #20 · Jun 21, 2010

KBIzzle shidizzle wizzle nizzle !

LOL - Sorry, I couldn't resist.

I have a very very similar project going on and I'm about to finish up. I would like to know how yours turned out and if you have had any moisture problems in your mini-attic area and did you go with vents in the mini-attic or did you seal it all off and go with a hot roof design? Hot roof, basically means you have no ventilation up in the attic.

I am thinking about going hot roof, because I have gone to much great length to air seal the shed off from the outside (lots of bugs around here) and I wanted it to be as efficient as possible energy-cooling-wise.

I am thinking about if I should put insulation over my ceiling sheetrock or just not put any, because I have radiant barrier laminated to the underside of the roof sheath/decking. Without a ceiling in there yet it seems to do pretty well temperature wise with no a/c assistance, but I am wondering how it will do after I put a ceiling in and it has less air to circulate and move with.

I was thinking, if i do it all like this, that maybe I could put 2 small ceiling vents, strategically placed, and my a/c would cool the workspace area and slowly vent/condition the attic area too...whilst all I'd have up in the attic is the radiant barrier on the roof decking and I was thinking about putting foamular insulation right above and in contact with the ceiling sheetrock sealed at the edges with spray foam.

There is not much space that would remain in the mini attic, so I really don't think it would impact my a/c bill much.

Here is a graphic of what space I'm dealing with and keep in mind that the ceiling/sheetrock/insulation don't exist yet.

See less See more

1 - 20 of 20 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.