Summer house - better to insulate or thicker walls?

Miss_Riot

ThisIsWeird said:

https://www.facebook.com/marketplace/item/186583450855832/?

Dead easy to line with 2" or 3" (nuts to go more) PIR.

That's more expensive than new! 

ThisIsWeird

What physical internal size does it need to be, MissR?
20 years ago I converted an attached single-block-skin garage into a room - it's where I have my PC. External walls battened with 2x1s, 1" Jablite (cheap expanded foam insulation) cut to fit in between, and 35mm insulated p'board - the thinnest -  screwed on top. (Garage shape - long and narrow - dictated the thin level of  side wall insulation.) So, 2" on the walls, one of which is poor value stuff (I do wish I'd bonded 2" insulated board straight on)
A couple of inches of Jablite on the concrete floor (in reality, due to the slope, it went from around 1" to 3"-ish, I think), and T&G floorboards on top, sanded and stained. The ceiling got a bit more insulation, possibly around 3" PIR.
The result is it's kept warm by the heat from my plasma screen, so around 200 W. It's been successfully used as a bedroom by mil, where the small CH rad kept it cosy with a luke-warm output.
I am not kidding when I say it's the easiest room in the house to heat, and the reason most likely is that it's draught-free.
So whilst I am not going to say that folks advocating 4" of insulation or it being made to meet building standards are wrong to do so - that would be ideal, of course - I am suggesting that if you line all the insides with 'just' 2" of PIR, to effectively make a sealed insulated box, you will - almost certainly - be able to keep that room cosy with, say, a 1kw oil-filled rad, and it'll only need to be turned up to max in the coldest spells.
Yes, windows and doors should be DG and seal well, but with a trickle vent position.
If you have a suitable type of roof, either 'flat' or gently sloping, then a skylight - essentially a DG pane sealed to a raised frame - will provide an astonishing amount of solar gain, even on dull days.
And, there are other ways to provide heating comfort such as electric seat covers.
£5k is not a lot. If you try and buy a new 'shed' for that, it won't be good quality, or be DG'd, or have well fitting doors, etc. Far better to keep an eye on FB, eBay, Gumtree or whatevs for a good 2nd hand one - they can be astonishing value, sometimes even free. Ditto for PIR - there's a steady amount of the stuff appearing around here.
Yes, a 2nd hand room will need dismantling, so you need to factor that in. If you cannot DIY, then either find a local handyperson, or engage family and friends for a day, laying on (weak) beers and sarnies! And a BBQ when it's rebuilt in your garden!
I can't see any other practical way. 

Good luck with this and your recovery. Meanwhile, Google images/Pinterest summer houses and garden rooms, and get ideas to make them look great inside! It should be a pleasant environment to be in

(Don't underestimate the insulating power of even 1" of PIR - it's astonishing stuff, and foiled on both sides. 1" is transformative. When you think about it, if that one inch has reduced heat transfer by a factor of, let's say, just 10, that means that only a tenth of the heat is coming through the far side. Ok, stick another inch on there - what additional improvement will that make? Yes, a tenth of a tenth. Ok, these figures are plucked from the air, but I am suggesting that 2" of PIR will provide superb insulation, and in such a circumstance as this - a temporary garden office of limited size on a budget - I'd put thicker only in the ceiling. If you CAN layer everything in 4", then great. If you cannot, then don't worry.

Miss_Riot

ThisIsWeird said:

What physical internal size does it need to be, MissR?
20 years ago I converted an attached single-block-skin garage into a room - it's where I have my PC. External walls battened with 2x1s, 1" Jablite (cheap expanded foam insulation) cut to fit in between, and 35mm insulated p'board - the thinnest -  screwed on top. (Garage shape - long and narrow - dictated the thin level of  side wall insulation.) So, 2" on the walls, one of which is poor value stuff (I do wish I'd bonded 2" insulated board straight on)
A couple of inches of Jablite on the concrete floor (in reality, due to the slope, it went from around 1" to 3"-ish, I think), and T&G floorboards on top, sanded and stained. The ceiling got a bit more insulation, possibly around 3" PIR.
The result is it's kept warm by the heat from my plasma screen, so around 200 W. It's been successfully used as a bedroom by mil, where the small CH rad kept it cosy with a luke-warm output.
I am not kidding when I say it's the easiest room in the house to heat, and the reason most likely is that it's draught-free.
So whilst I am not going to say that folks advocating 4" of insulation or it being made to meet building standards are wrong to do so - that would be ideal, of course - I am suggesting that if you line all the insides with 'just' 2" of PIR, to effectively make a sealed insulated box, you will - almost certainly - be able to keep that room cosy with, say, a 1kw oil-filled rad, and it'll only need to be turned up to max in the coldest spells.
Yes, windows and doors should be DG and seal well, but with a trickle vent position.
If you have a suitable type of roof, either 'flat' or gently sloping, then a skylight - essentially a DG pane sealed to a raised frame - will provide an astonishing amount of solar gain, even on dull days.
And, there are other ways to provide heating comfort such as electric seat covers.
£5k is not a lot. If you try and buy a new 'shed' for that, it won't be good quality, or be DG'd, or have well fitting doors, etc. Far better to keep an eye on FB, eBay, Gumtree or whatevs for a good 2nd hand one - they can be astonishing value, sometimes even free. Ditto for PIR - there's a steady amount of the stuff appearing around here.
Yes, a 2nd hand room will need dismantling, so you need to factor that in. If you cannot DIY, then either find a local handyperson, or engage family and friends for a day, laying on (weak) beers and sarnies! And a BBQ when it's rebuilt in your garden!
I can't see any other practical way. 

Good luck with this and your recovery. Meanwhile, Google images/Pinterest summer houses and garden rooms, and get ideas to make them look great inside! It should be a pleasant environment to be in

(Don't underestimate the insulating power of even 1" of PIR - it's astonishing stuff, and foiled on both sides. 1" is transformative. When you think about it, if that one inch has reduced heat transfer by a factor of, let's say, just 10, that means that only a tenth of the heat is coming through the far side. Ok, stick another inch on there - what additional improvement will that make? Yes, a tenth of a tenth. Ok, these figures are plucked from the air, but I am suggesting that 2" of PIR will provide superb insulation, and in such a circumstance as this - a temporary garden office of limited size on a budget - I'd put thicker only in the ceiling. If you CAN layer everything in 4", then great. If you cannot, then don't worry.

Size wise a minimum of 12 x 8. But that's absolute minimum - we need to make sure there is turning circle for my wheelchair so that I can come in and turn around if needed. 

My partner has friends who are happy to come help insulate and board it, but we still can't work out if we need 18mm, 28mm or even thicker walls even with PIR insulation. We have looked at ready insulated ones, those are out of our budget. Most we are looking at are toughened glass - then there's UPVC, which is even more, but our preferred option. I don't know if installing secondhand units would be an option? Secondhand Summerhouses- we have gone to look at several to find they were half rotten and not worth buying, or like the one posted on here before, they're being sold for nearly new prices. 

It's an absolute minefield and my partner is feeling totally overwhelmed with options so I have mostly taken over trying to sort it out with limited capacity. 

ThisIsWeird

Unless you manage to buy a purpose-made insulated unit - like one of the lift-in examples I linked to, then I'd suggest you don't concern yourself about wall thickness. Yes, a thicker-walled 'house is always going to be better in terms of strength and rigidity, but it's unlikely to have a huge bearing on insulation value.

So, if you are going the 'buy a nice 2nd-hand summer house and insulate it' route, then just look at the overall quality and condition of the ones available, and don't bother about the insulation value of the timber walls - you're going to be adding that

Although DG is pretty much a 'must', I wouldn't dismiss a SG example if it ticks all the other boxes. SG will be fine for most of the year, and different methods of cheap secondary glazing can be added for the freezing months. 

Tbh, I suspect your options will be limited to 2nd hand for a 'house of any usable quality - what can you get for £5k new? 

Good luck. There are/will be some great options out there - just keep looking

doningtonphil

I used simplysips.co.uk. Floor, 3 of the walls and roof are all made using SIPS panels (80mm Kingspan sandwiched between OSB boards).  Front wall is a sliding patio door.  I got a Kingspan metal clad roof deom the supplier tha built our first garden room, but I imagine the EPDM rubber roof would be OK - very common method.

The panels arrive on the back of a trailerand are numbered, with building plans.  A friend who is a joiner helped me build mine

We built the 2nd one for much less than we had the first one built for.  The patio door faces east so solar gain in the morning (when the sun shines) is good.  Apart from that a 1kw panel heater is enough to warnm the room up promptly (2.4x2m).  Easy to keep warm