Summer house insulation ceiling or roof

kowalski181

Hello
Some hot days recently and am baking in summer house I now use as office. All the heat is coming through the roof. Have seen some previous posts and people seem to do this two ways. One is to insulate the roof, I would take off shingle slates, leave felt underneath, put on 25,mm insulation board, then some 9mm osb, before covering with some new felt and binning the shingle I had on before. Or I could use indoors some superquilt in ceiling or insulation boards and do it that way. The interior option seems a bit more difficult as will need more batons for air gap and then MDF to finish and will likely be dearer. Am I on the right track here and would I have any problems. Will my roof be ok as isn't thickest .. to put boarding and osb on top

Megaross

Either way should be fine from what you've described but you may still experience some issues with damp during the colder months.

kowalski181

Cheers, I think indoor option would be easier, just need to put some more wood on the ceiling edges , doesn't need a membrane on the ceiling does it? I just need to make sure is small gap from ceiling to board then again for board covering 

Megaross

So you'll need a cold space of approx 50mm to allow the roof to breathe, then your insulation boards, then a membrane, then your cover material - osb or whatever you want to use.

My concern however would be the walls if uninsulated would then become a condensation trap.

How is the summer house constructed?

kowalski181

It is a typical Wooden summer house, with two double glazed windows and a double glazed double door. Aha I did read about the membrane what would you recommend. It gets condensation on windows in the winter at the moment. I am hoping it helps reduce Temps in summer and but warmer in winter 

casper_gutman

My roof makeup is tongue and groove boards, 50mm Kingspan-type insulation over that, then roof shingles directly on top of that - no other boarding like OSB or ply over the insulation. It's simple and seems to be pretty widely used. I did wonder whether a breathable membrane would be beneficial somewhere in there, but saw lots of people saying they didn't bother. I haven't noticed any issues so far.

Personally I'd stick with shingles for the combination of aesthetics and durability if I could possibly afford the extra outlay and the time to fit them. It also makes omitting any boarding over the insulation a more viable option as the shingles are nailed at close spacing. I reckon you'd be more likely to run into trouble attempting this with felt, as it wouldn't bond well to the foil surface of the insulation and you don't want to be whacking nails through every foot or so.

In my case the summerhouse is a log cabin with 2" thick solid timber walls. I haven't done anything more to insulate them and have no issues with condensation, but then the thickness of the material provides a fair bit of inherent insulation. 

kowalski181

So take shingles off, put  50mm boards on top of felt. Then get shingles have taken off and put back on top off ins boards??

Bendy_House

What is the EXACT construction of your roof, Kow? I assume it's pitched? Vaulted inside? 

And walls are what?

If you are suffering from condensation, you need to ventilate - a couple of windows on 'trickle', for example. If the room is poorly insulated, tho', then this won't help to keep it warm. 

kowalski181

some pictures 

kowalski181

some pictures

casper_gutman

kowalski181 said:

So take shingles off, put  50mm boards on top of felt. Then get shingles have taken off and put back on top off ins boards??

Pretty much this. The bit I'm not sure about is the idea of reusing the shingles: they'll have sticky tarry stuff on the back and probably three nails in each shingle strip, and I'm not sure you'll get them off intact.

I've never removed shingles from a roof but heard the best way was to use a long-handled tool like a spade to get under them and lever the nails out. In the US where shingled roofs are common on houses, they use a thing like a spade with teeth, e.g. https://www.amazon.com/Shingle-Stripper-Fiberglass-MBI-Tools/dp/B07Z874TBQ.

Once the shingles are off, the method I used to insulate and re-cover was as discussed here: https://www.tuin.co.uk/blog/insulating-a-log-cabin-floor-and-roof/ (you can ignore the bit about insulating the floor for now - your cabin walls are probably too thin for it to be usable in the winter, and I think it's the roof insulation which will help keep summer temperatures down).