Insulation thickness for walls?

[Hsmith192]

Hi guys,

I have. 6m x 3.5m garage and have outside access to 3 of the walls.

I would like to insulate the walls but want to not eat into the space too much.

What insulation thickness is suitable for insulating an out building garage?

 

[AJS2018]

I used 100mm and after this winter I’m pleased I did, The outside overnight temperature has been as low as -5 and providing I’ve used the workshop the day before, it has never dropped below 12, the heating is turned off at 5:30pm. It’s a converted double size garage with insulation in the roof as well, also feels cool when it’s very hot in the summer.

 

[Rorschach]

Is the roof insulated? Are your openings sealed up? How will you heat the space?
Waste of time insulating the walls until these things are done.

 

[Ollie78]

Any insulation will help.
Depends what insulation it is.
100mm of celotex is going to be more insulating than 100mm of rockwool.
Also there is a value calculation, celotex is way more expensive.
I am extending my workshop (it's inside a barn) . I have found the best bang for buck for me was 100mm cavity batts in my stud wall.
Make sure to do the roof first.


Ollie

 

[Hsmith192]

Is the roof insulated? Are your openings sealed up? How will you heat the space?
Waste of time insulating the walls until these things are done.

Hi everyone,

Roof has polystyrene based insulation fitted under the corrugated section.

I might need to replace that too as it wasn’t too great.

I’m using a 2000w fan heater but I would like to keep the heat in a bit more.

Thanks for your replies everyone.

Roof will be a priority.

 

[Tazio]

The first place to start is the roof Poly is pretty poor go with at least 100mm of celotex in the roof and if you need to cut down then 50mm on the walls and if you have a concrete floor perhaps 50mm there then cover with sterling board .. i would though start with the roof as thats where most heat loss happens ....

 

[gcusick]

In general, some’s good, more’s better.

 

[Hsmith192]

Thank you, can anyone suggest a good type of insulation for the walls? Rock wool? Slab or roll?

 

[SBD]

Don't dismiss the ally foil products, I've got the roof and a wall still to do (last roll arriving today) but for the first time that I can ever remember the thermostat has started kicking in on the fan heater.
Bang for your buck m2 wise ease of use etc is spot on. Just make sure it has the correct fire regs though, the really really cheap stuff can be dodgy. Bubble wrap is great... for starting fires! I'd get that poly out of your roof pronto too.

 

[Tazio]

Thank you, can anyone suggest a good type of insulation for the walls? Rock wool? Slab or roll?

celotex ..Rock wool is a poor insulator and tends to slide if not fitted propearly in the walls ..you only do these jobs once so I always work on doing the best you can !.
aluminium foil products are fine but need careful fitting to maximise efficiency we have done barn conversations using iso super products but the foil products require passive air spaces and non compressive fitting ..

 

[Hornbeam]

You will lose heat out of the building in 3 ways
Conduction through the roof/wall
Cold air infiltration which then needs to be heated
Conduction through building details and cold bridges through the insulation
Thermal conductivity of rock wool/glass wool is about 0.04, expanded/extruded polystyrene is about 0.03 and PIR board (celotex etc) about 0.024. So in simple terms you need nearly twice the thickness of glasswool compared with PIR. I wouldnt use polystyrene due to fire risk.
PIR at 100mm has a U value of around 0.2 so that means that for every square metre you will lose 0.2Watts of heat per degree difference inside to out
A concrete floor slab has a U value of about 1 excluding edge effects
Your building has 21m2 of roof, about 45m2 wall depending upon which wall is shared and 21m2 of floor
So on a day where it is 0 outside and you want 20'C inside you will need 20 ((21X0.2)+(21 X 1.0) + (45X 0,2)) 700watts of heat. As a general simple rule if your building isnt too air leaky I would double this for cold air infiltration (If you have an opening garage door these are really bad so look at how you can seal it.
So your 2kW fan heater should be about right.
If your roof space is open then air can stratify with all the warm air in the roof space. a small fam or a microclean filter type unit will reduce this
Ian

 

[Jelly]

celotex ..Rock wool is a poor insulator and tends to slide if not fitted propearly in the walls ..you only do these jobs once so I always work on doing the best you can !.

Rockwool isn't as good an insulator as PIR, but it's still pretty good as insulating materials go.

It's advantage however is that it's both orders of magnitude cheaper, and far and away the superior product for sound deadening.

I went with it because the sound insulation was important for me and found that it performs very well for thermal insulation too.

But I wouldn't argue that it's not as easy to make a good job of though, it's a right bugger to install by comparison to PIR.

 

[DBT85]

I only put 60mm of PIR in the walls on mine and 120mm in the roof.

 

[Amateur]

I used King Span products...great for blocking off a garage door from the inside too.
Take a look at their site.
I'm not sure if they are making timber faced wall insulation which would cut down on the time to fit your space out.
Don't forget if you do have a garage door don't seal it so you can't at some point Get that 40 foot yacht outside that you've just built, which you just realise won't fit through the side door.!!
Be cheeky and send them some dimensions with a marked up drawing and tell them what you want to achieve.I
I'm sure they'd help

 

[Hornbeam]

On this building the wall are about double the roof area so more important. The other thing I would do is invest in some good quality floor matting. It will improve the floor slab insulation but will also make it feel warmer

 

[Tazio]

I used King Span products...great for blocking off a garage door from the inside too.
Take a look at their site.
I'm not sure if they are making timber faced wall insulation which would cut down on the time to fit your space out.
Don't forget if you do have a garage door don't seal it so you can't at some point Get that 40 foot yacht outside that you've just built, which you just realise won't fit through the side door.!!
Be cheeky and send them some dimensions with a marked up drawing and tell them what you want to achieve.I
I'm sure they'd help

 

[Tazio]

What you mean like this ..yep next project ....

 

[Amateur]

What you mean like this ..yep next project ....

I can see it now sailing into the sunset

 

[bryan267]

I’ve insulated two now, i use 25mm cellotex on the walls, between a 2x1 frame screwed to the walls, then either plaster board or ply covering. The ceiling i used 100mm the first one, my second one i wrapped 25mm polystyrene in a foil sheet so that if rain ever got in it would run the length of the insulation into the overhang space where my soffits facias are and then out the vents. Thats the hope anyway. I would say the 100mm was noticably better before the ceiling went on, but my roof space above the insulation is very well ventilated and the high winds where moving the insulation, however since the ceiling went on the pressure changes from wind have gone and its far more effective now. I have tube heaters, about 360watts total and i leave the thermostat at 12 degrees permanently. I didnt notice my electric go up when i switched this all on in december, obviously it must have but it cant be by much. Mine is small, 4m x 5m, with flat roof but its free of any draughts, its 12/11 degrees when i walk in and me being in there working soon warms it up, but I have a 1k panel heater for just in case, I’ve only used it a few times. I find its easier to retain a low heat than to let it go cold and try to heat it when you need it. I dont know what made me pick 12 degrees for the thermostat I guess i wanted more than just damp out, and didnt want it to feel cold when i walked in, 12 may feel cold when the weather warms up, but it doesn’t now.

 

[mikej460]

I only put 60mm of PIR in the walls on mine and 120mm in the roof.

I'd be interested to know what it has been like working in it over this winter? Do you know the minimum temp it went down to inside at all?

thanks

Mike