# How to insulate a ceiling in shed-house



## Karen

We are converting an amish shed into a cottage to be used now for our son in college. It's a barn-style shed like in the photo below.

We have everything figured out except on what would be the best way to insulate the ceiling and how best to not have moisture problems. Also, do we do anything with the vent in top? If not, won't it be difficult to heat and cool the building? Additionally, cost is also a factor as we're on a shoestring budget for this one. We're in Virginia, zone 6B


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## wy_white_wolf

Do you plan on putting in ceiling joists and making the top part an attic? or finishing off at the roof rafters?

If installing joists then the isulation can be layed or blown in on top of them. You would also leave the vent open.

If finishing off to the rafters you have a few problems. You'll need to leave 1" of air space between the insulation and OSB and somehow vent that space. Most likely you need to redo the soffits and center ridge to install the vents. This option may not be availble if they didn't design the soffits with a place to install the vent. Ridge vent would just require removal of the ridge cap, install a ridge vent and new ridge cap. You would also need to plug off the wall vent then. 

You could have it spray foamed with a closed cell foam and not have to leave the air space or vent it. If I went that route I'd also just foam the walls to after all plumbing and wiring are done. You may also want to foam the underside of the floor.

Another option would be to tear the roofing off and install foam boards under a new roof.

WWW


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## haypoint

Put up Styrofoam sheets between the studs and joists. Then put an inch or two Styrofoam (blue) sheets over the walls and ceiling. Then cover it with cheap paneling.
Add a window air conditioner and an electric space heater.


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## pips

i like the sheet foam idea and chaulk the edges.u could use fiberglass but will require framming


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## Cookie2

Does the building currently have a roof? There is sheet insulation that you put on top of the roof's tar paper then you shingle or put a metal roof on top of that. If you have an existing roof that you don't want to re-do, then I agree with making a small attic space - leaving the vent open to allow for air flow so you don't ice built up or ice damning. Insulate between the studs with roll batting (which will also reduce noise) and make sure you put down and insulation of some sort on the floor. If you can get under the building, I'd just put spray foam between the floor joists. If it is on a slab, I'd put down a rubberized barrier then carpet over it.

Make sure the building has it's own electrical ground. Will you be putting in plumbing, too?


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## Karen

To answer some questions, it looks just like the photo above and has a metal roof on the outside. We will be wiring it, but it will have no plumbing for now. No attic. 

I'm liking the foam board idea, but the recommended R-rating for roofs here is R49. It doesn't have to be that high, but we would like to have it as high as we can. Can we accomplish any where near that with foam board?

I'm so ignorant when it comes to this stuff, but could we just staple on regular fiberglass insulation to those rafters and then cover it with plywood or OSB?


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## wy_white_wolf

Adding 2 by 2 nailers mooney wall style would give you about an R35 with the low thermal bridging using spray foam. Without tearing off the roof to add foam board under it I just don't see getting any closer to R49 than that.

WWW


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## Karen

I'm confused. The roof now is just metal roofing with plywood under it. Can't we just use regular roll batting insulation stapled to the ceiling, or foam board and then insulation?


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## wy_white_wolf

Karen said:


> I'm confused. The roof now is just metal roofing with plywood under it. Can't we just use regular roll batting insulation stapled to the ceiling, or foam board and then insulation?


Is the metal roof self venting with no tar paper under it?

If yes, you can just install batts but the about the highest R value you will get is 13.

If it's not self venting or they put tar paper under the metal you would have to create and vent an airspace as I mentioned in post 2 to use batts or foam boards. The air space will take away from the room for batts so you would be lucky to get end up with R9.


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## Cookie2

From personal experience ... if you try to insulate the roof, then when it snows (and it will), the snow will at first pile up on the roof then begin to melt. The roof won't be cold enough to keep the snow from melting. As the roof moves to the edges, then there won't be a roof to warm it anymore and the water will re-freeze, causing dangerous icicles and ice damming. The water flowing down the roof will back-up against this icy edge and find a place to go - usually inside or down the inside of the walls. It all becomes a wet mess.

So to prevent ice damming, most people opt to keep the roof cold by creating some kind of uninsulated attic space. The insulation is on top of the interior ceiling so warmed air inside the living space doesn't migrate to the attic. This way the snow melts off the roof when the weather gets warmer and the water won't re-freeze in the cold air.

Even houses with cathedral ceilings typically have an air space between the ceiling layer and roof. In our portion of the house that has a cathedral ceiling, air enters under the eaves and vents along the ridge line (ridge line venting is cheap and I recommend this method for finishing your shed roof - it'll help cool the attic space and preserve the roof.) Houses where the ceiling and roof are solid layers to make one unit tend to be problematic or have multiple layers of insulation. Even then, the only time I've seen this work was in when we lived in CA and rarely saw freezing weather (even then it was a pain).

The roof doesn't have to be even with the walls. You could raise the roof to the 'hip' in the roof.


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## Harry Chickpea

You don't give a width or interior height.

If the wall studs are standard 8' 2"x4"s, then the ceiling is easy peasy.
Get metal joist hangers and enough 2"x4"s of the proper length to span the shed just below the gambrel, one for each rafter plus two for the ends and two for along the long walls.

Attach a ring of 2"x4"s around where those two existing 2"x4"s are at the base of the roof.

Attach a joist hanger to the ring 2"x4"s, one on each side directly under each roof rafter.

Measure and cut the 2"x4"s that will cross the room and hang in those joist hangers.

Place them in the joist hangers with any "crown" or bowing facing up.

In the center of the roof gusset, drive a 10d nail. Do the same in the center of the 2"x4" directly underneath it.

Join the two nails with high tensile fence wire or the correct wire sold at the box stores for hanging ceilings.

At this point, you will have crossbeams of 2"x4"s supported on each end with joist hangers and in the center with wire from the top gusset. That should easily support a basic ceiling.

Buy 5/8" sheetrock to cover the bottoms of the 2"x4"s and the ring of 2"x4"s to make a standard ceiling. 

As you are installing the sheetrock, place your fiberglass batt insulation on top of each secured sheet.

Make an access door wherever you think best. Center of a room is common.

Tape and mud the sheetrock.

Why do I suggest this method?
1. If you have an occupied living space, it is not only prudent to reduce fire risk, but if an inspector or zoning person comes around you will be less likely to have to tear your work out.
2. Foam in a small space is a death sentence in a fire.
3. The process is incredibly cheap and with a good result and high insulative value.
4. Removal is a simple process if it becomes necessary. 
5. Only the sheetrock would not be easily recycled, but that can be added to the soil as a soil amendment.

Edit to add - there will be a small amount of condensation under the 2"x4"s if the insulation doesn't completely cover them. The wood is a better conductor of heat than the insulation. Either cover completely with insulation or use lath going 90 degrees to the 2"x4"s and attach the sheetrock to the lath.


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## haypoint

Karen said:


> I'm confused. The roof now is just metal roofing with plywood under it. Can't we just use regular roll batting insulation stapled to the ceiling, or foam board and then insulation?


Roll batting/fiberglass won't get you nearly as much R as blue board, per inch. Figure 5 R per inch. So, 3 1/2 inches between the 2x4 roof rafters gets you to 17 1/2 R. Then use 2 inch sheets over the rafters to get you to 27 1/2 R It takes about 9 1/2 inches of fiberglass bats to get you R30.

With a shingle roof and a low sloped roof, you could get water backing up and getting into the walls. But you have a steel roof and a steep pitch. No ice dams.


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## RonM

A metal roof on a small building like that? Never saw a metal roof on that style building in this area..and metal would not go over plywood, it would be on nailers...


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## RonM

The reason I question this , they build a few of these buildings around here and their goal is cheap and fast. Metal roofing is neither....


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## NorthernMich

best?

in my opinion-spray on foam from a contractor

Get estimates, this crew was 50% lower than the one a buddy recommended and sprayed thicker than contracted to.

I love it!


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## wharton

RonM said:


> A metal roof on a small building like that? Never saw a metal roof on that style building in this area..and metal would not go over plywood, it would be on nailers...


 There are plenty of small sheds in the northeast with metal roofs ,and there is no reason that the metal has to be installed on nailers. I've screwed lots of it down over 5/8" plywood, or OSB, with a layer of felt between.


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## robsdak

NorthernMich said:


> best?
> 
> in my opinion-spray on foam from a contractor
> 
> Get estimates, this crew was 50% lower than the one a buddy recommended and sprayed thicker than contracted to.
> 
> I love it!


this was my suggestion as well. i have a friend that built one and used the this type. http://tigerfoam.com/sprayfoaminsulation/ easy to do and the savings with the electric bill was awesome.


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