Insulating summer house roof ideas

[fastbikes76]

In recent warm weather I have noticed on my app that the temp went as high as 37 degrees internally. That is with everything closedown day and blackout blinds on all the windows. The summer house roof gets full sun from sunrise to sunset and is only 19mm T&G, I’m guessing this is where majority of the heat is coming from as the wall logs are 44mm thick and windows are double glazed.

What would be the best way to insulate this without covering the purlins ? 25mm celotex or would 50mm jablite EPS be ok ? I’m guessing some form of battening to hold boards up once cut between purlins and then something to cover the insulation. Again we like the look of the T&G roof but replicating that under insulation will soon add cost and work to the job.

Any ideas how you would do it?



Cheers
Fb

[magooagain]

I put my 100mm rigid insulation on top of the roof inbetween rafters that I laid onto the existing felt roof.
Then I boarded over the rafters and then put a tin roof on top.

This has enabled me to keep the T&G ceiling in the cabin.

[fastbikes76]

magooagain said:

I put my 100mm rigid insulation on top of the roof inbetween rafters that I laid onto the existing felt roof.
Then I boarded over the rafters and then put a tin roof on top.

This has enabled me to keep the T&G ceiling in the cabin.

That's the best way and tbh I wish I had done that. Unfortunately when buying mine I was give the speech about not needing heating or anything because the wall logs were so thick and I had double glazing. What they didn't take into account was the amount of heat that comes IN through the roof.

So now I'm at the 'doing it the hard way' position while trying to preserve the interior looks. Someone else also mentioned rockwool between roof and another layer of boarding between purlins. Just need to know which is best I guess.

[Equus]

fastbikes76 said:

...I’m guessing this is where majority of the heat is coming from as the wall logs are 44mm thick and windows are double glazed.

Very basic (primary school level) physics: heat is transmitted by conduction, convection or radiation.

At risk of stating the bleeding obvious, windows let in light, and light (in the infra red spectrum) is how the sun transmits its heat to us, by radiation.

Whether the windows are double glazed or not therefore makes bugger all difference to whether solar energy gets in; it merely reduces the energy from the warm air inside being transmitted back out (which occurs mainly by conduction and convection).

Depending on which direction the glazing faces, it could well be that the glazing is actually the most significant contributor, and all adding insulation to the roof will do is prevent the solar gain escaping. In that case, the most effective solution would be external solar blinds, shades or a brise soleil on the windows; or addition of a solar reflective film..

What is the roof covered with? If it's aesthetically viable, a more effective solution to reducing solar transmission through the roof may be to use a lighter coloured roof surface, which reflects the light (heat) before it ever gets in (but still allows heat from within to radiate out).

[gizlaroc]

I would staple Superquilt to the rafters, batten out and then put tongue and groove back over the top and paint.

That will give you the same as roughly 125mm Celotex with a nice cavity in between as well and take up very little space.

[jeff m2]

You can have all the insulation in the world, but at some point you are going to open the door, let in the heat and trap it inside!
(then continue to let it cook)

Ventilation I think might be more practical..
Either a ridge vent, or an insulated drop ceiling with open eaves and an extractor fan to pull out the hot air from what would in effect be a small loft space.
Thus eliminating conductive ceiling heat

[fastbikes76]

Equus said:

Very basic (primary school level) physics: heat is transmitted by conduction, convection or radiation.

At risk of stating the bleeding obvious, windows let in light, and light (in the infra red spectrum) is how the sun transmits its heat to us, by radiation.

Whether the windows are double glazed or not therefore makes bugger all difference to whether solar energy gets in; it merely reduces the energy from the warm air inside being transmitted back out (which occurs mainly by conduction and convection).

Depending on which direction the glazing faces, it could well be that the glazing is actually the most significant contributor, and all adding insulation to the roof will do is prevent the solar gain escaping. In that case, the most effective solution would be external solar blinds, shades or a brise soleil on the windows; or addition of a solar reflective film..

What is the roof covered with? If it's aesthetically viable, a more effective solution to reducing solar transmission through the roof may be to use a lighter coloured roof surface, which reflects the light (heat) before it ever gets in (but still allows heat from within to radiate out).

The windows have blackout blinds fitted to both windows and doors, should that not keep majority of the heat out. At a very basic level when touching the roof boards from inside they are pretty warm ! The inside wall logs and windows are not... this makes me think most of the heat is coming from the baked roof. I get the point that external blinds may be better. I have a friend who specialises in window films so may ask him regarding some form of solar reflective film.

Roof is quite a light green colour felt already rather than a dark sun soaking colour

gizlaroc said:

I would staple Superquilt to the rafters, batten out and then put tongue and groove back over the top and paint.

That will give you the same as roughly 125mm Celotex with a nice cavity in between as well and take up very little space.

Will look into superquilt, not heard of it before

jeff m2 said:

You can have all the insulation in the world, but at some point you are going to open the door, let in the heat and trap it inside!
(then continue to let it cook)

Ventilation I think might be more practical..
Either a ridge vent, or an insulated drop ceiling with open eaves and an extractor fan to pull out the hot air from what would in effect be a small loft space.
Thus eliminating conductive ceiling heat

It has a small vent front and rear but that obviously does the grand total of bugger all.

Opening the doors and windows drops the heat very quickly, just don’t fancy having a TV, amp and fridges trying to survive near 40 degree heat !

Conversely, if I’m gaining this much heat, I’m also losing all the heat I put in during winter. Need to borrow the thermal camera from work and have a look at losses or gains

[gizlaroc]

fastbikes76 said:

Will look into superquilt, not heard of it before

This thread shows what it is about.

I am now 5 years in and still amazes me how well it keeps the heat out. Our windows our south facing too.

https://www.pistonheads.com/gassing/topic.asp?h=0&...

[Little Lofty]

Superquilt/Tri iso etc is a good product. I used it on a few lofts for a while (before building control got twitchy) it definitely keeps heat out. A friend of mine used it on his conservatory roof and it made a massive difference.

[samdale]

fastbikes76 said:

The windows have blackout blinds fitted to both windows and doors, should that not keep majority of the heat out.

Depending on what they're made of/backed with, you may have essentially just made a solar powered radiator. Dark/dense material is probably doing more harm than good.

[fastbikes76]

gizlaroc said:

This thread shows what it is about.

I am now 5 years in and still amazes me how well it keeps the heat out. Our windows our south facing too.

https://www.pistonheads.com/gassing/topic.asp?h=0&...

Thanks, will price some up .

samdale said:

Depending on what they're made of/backed with, you may have essentially just made a solar powered radiator. Dark/dense material is probably doing more harm than good.

A fair point well made, they are black which probably isn’t helping haha.

First step will be pic up thermal cam from work and wait for next sunny hit day I think. Then I can work out where the heat is coming from mainly.

Fb

[magooagain]

My cabin is as modern as your on the inside OP,but I didn't like the outside modern look. The walls and floor are also insulated with100mm rigid insulation.
Then I re clad the external walls in a rustic style.

I also have shutters etc.

Here is how it looked when finished. There are grape vines growing over the front now.

[CustardOnChips]

Might be worth speaking to a professional about it before committing to a solution. Could save you money in the long run.

[DonkeyApple]

Would seem a shame to change the interior look.

How would the roof look if you fitted insulation on the outside like they do on flat roofs and changed any decorative woodwork that’s on the frontage etc to accommodate it?

[bobtail4x4]

Little Lofty said:

Superquilt/Tri iso etc is a good product. I used it on a few lofts for a while (before building control got twitchy) it definitely keeps heat out. A friend of mine used it on his conservatory roof and it made a massive difference.

two houses near me, one had tri iso in its loft conversion, the other has kingspan,

first snow of the year, and only one still had snow on the roof, not the tri iso one, its crap.

[kurt535]

Go on Tuin log cabin website; i am sure the owner published an article on there why you should avoid insulating from the inside.

[DonkeyApple]

magooagain said:

My cabin is as modern as your on the inside OP,but I didn't like the outside modern look. The walls and floor are also insulated with100mm rigid insulation.
Then I re clad the external walls in a rustic style.

I also have shutters etc.

Here is how it looked when finished. There are grape vines growing over the front now.

That’s very nice by the way. Has a very subtle style. Bin chance with the 2019 vintage.

[fastbikes76]

Picked up the Flir thermal camera from work and had a little play around today. Current ambient temp is around 15ish and partly cloudy with sunny bursts. The sun rises slightly behind the summer house and moves round from behind, round the left side and sets pretty much directly in front. As such the right hand side of the roof gets full sun all day. Some pics below show the roof is 100% the source of any excess heat coming in (or going out in winter) .

Right hand side of roof with purlins visible


44mm thick side walls immediately below roof show no signs of heating up


Blackout blinds warm but not allowing in any heat


Blackout blinds on doors in full sun at the moment and again warmer but no leaching through the sides


Wall logs between windows and doors cool despite being in direct sun.


RHS roof warm as hell still


Absolutely zero heat leaching in past blackout blinds


Again no excess warmth from anything other than roof.


So in conclusion, windows and blackout blinds don’t appear to be an issue at all even though in direct sunlight all day. The major issue is 19mm T&G roof boards not being man enough and the big old roof felt acting as a lovely sun soaked. I guess best way forward will be rip felt off, lay a membrane down, lay 50mm celotex boards on top of that and then refelt. I have central heating in there which is set too keep it a minimum of 10 degrees all year round, last winter I had not a single drop of condensation and don’t expect any with keeping it at a constant temp.

Fb

[TriumphStag3.0V8]

When I built my cabin, I put 50mm Celotex insulation on top of the roof boards (which are the same as yours), then fixed the shingles on top of these, and made the edges up with additional boards to cover the edges, stained to match the cabin. This does a good job of keeping the heat out of the roof as I have the same shingles on my store-shed which has no insulation. The difference is noticeable.

[gizlaroc]

bobtail4x4 said:

two houses near me, one had tri iso in its loft conversion, the other has kingspan,

first snow of the year, and only one still had snow on the roof, not the tri iso one, its crap.

I would argue it was installed incorrectly then.

During the snow our main roof, recently insulated and retiled melted will before the conservatory roof with Superquilt.

It needs to be airtight and have at least a 40-50mm gap between roof and quilt.