Insulating Outbuilding Shopping List

[hamd01]

Im just in the process of planning and getting to order materials to insulate and get an outbuilding ready to plaster.

Id be interested to hear if you guys think my calculations are sounding about right. The area is around 10m x 4m, and below is my shopping list for the insulation/plasetrboard.

I was planning to buy the kingspan from a seconds retailer who seem to be well recommended on these forums). Must admit, the cost of insulated plasterboard surprised me!

Item	Cost
Plasetrboard Screws	£20
Insulation tape	£20
Insulated plaster board	£1,353
Studs battons	£210
vapour sheet	£90
Kingspan wall insulation (100mm)	£570
Kingspan floor insulation (100mm)	£600
osb sheets for floor	£500
Total	£3,363

Ive not included absolutly everything....sundry wise, but would be interested to hear if you guys think my list is about right...or not?

Cheers

 

[Charlie George]

100mm kingspan on walls+insulated plasterboard? sound overkill, what about the ceiling?

 

[SFK]

Diyer here who has done this to outside building... Why have insulated plasterboard when you have 100mm insulation ?

And why have vapor sheet (for the floor?) when you have foil on insulation that is taped up. ?

And don't forget to insulate ceiling.

Need to include cost of plasterer to skim plaster room.

And include cost of electrics (working for sockets, ethernet and light switches. )

 

[hamd01]

100mm kingspan on walls+insulated plasterboard? sound overkill, what about the ceiling?

Ill be honest....I did wonder if it was overkill. Would you just 100m kingspan and then standard plasterboard?

The ceiling is lofted (former barn), but thankfully has alread had velux put in and been insulated by the previous owners. It was a bit of a hobby/games room, but bare brice and whitewashed....Im looking to make it into a proper daily use space.

 

[hamd01]

Diyer here who has done this to outside building... Why have insulated plasterboard when you have 100mm insulation ?

And why have vapor sheet (for the floor?) when you have foil on insulation that is taped up. ?

And don't forget to insulate ceiling.

Need to include cost of plasterer to skim plaster room.

And include cost of electrics (working for sockets, ethernet and light switches. )

Thanks mate. I think I have missunderstood somthing in my research. I though that I would need the kingspan and the insulated plasterboard..... but since your the second person in 5 minutes to question it....im now thinking its over the top! Would you just batton, fill with kingspan and then standard plasterboard?

Ceiling is thankfully already done, and electrics are alread in there.... obviously quite a bit of work on that front to bring sockets over the new board etc.

Thanks for your advice.

 

[SFK]

With regards to insulating a 'house', this might be useful background reading (I have done similar):
SFK

https://jack-kelly.com/insulating_our_victorian_living_room

This shows battons / stud filled with insulation which is what I did.

But
You can also put single layer of 100mm insulation plasterboard adhesive glued on wall and joined with metal tape. Then battons/stud (turned sideways to reduce depth off wall) floor to ceiling. And normal plasterboard on this. And use the air gap for cabling, or fill with more insulatio. This is cheaper than insulated plasterboard.

 

[drpepe]

With regards to insulating a 'house', this might be useful background reading (I have done similar):
SFK

https://jack-kelly.com/insulating_our_victorian_living_room

This shows battons / stud filled with insulation which is what I did.

But
You can also put single layer of 100mm insulation plasterboard adhesive glued on wall and joined with metal tape. Then battons/stud (turned sideways to reduce depth off wall) floor to ceiling. And normal plasterboard on this. And use the air gap for cabling, or fill with more insulatio. This is cheaper than insulated plasterboard.

Would you fix the battens into the wall through the glued on insulation? What fixings would you use?

 

[big-all]

just a though
is this out building to be just a useful space or up to building regs as a habitable room and possible extension to be included as part off the house ??

just a thought

 

[noseall]

100mm kingspan on walls+insulated plasterboard? sound overkill, what about the ceiling?

A secondary layer (across the studs or joists) is essential. No matter how good the insulation is between the timbers, there is always the risk of condensation shadowing occurring, with cold transfer through the timbers.

 

[hamd01]

A secondary layer (across the studs or joists) is essential. No matter how good the insulation is between the timbers, there is always the risk of condensation shadowing occurring, with cold transfer through the timbers.

So you think insulated plasterboard is needed to? wouldnt the vapour sheeting deal with the condensation?

 

[SFK]

Would you fix the battens into the wall through the glued on insulation? What fixings would you use?

To minismise thermal bridging, I would put 100mm PIR on the walls, and then studs to hang the plasterboard, I would put a base plate and top plate on the floor and ceiling and put studs between these. See here for an image:
https://www.carpentry-tips-and-tricks.com/Interior-wall-framing.html
Basically a free standing stud wall infront of your PIR boards.
Then put in cables.
Add another layer of insulation between these studs where there are no cables.
And then normal plasterboard.

It should be noted that this method uses a lot of space.
You were on PIR + Insulated plasterboard = 100 + (25? + 12) = 137mm (125mm of insulation but might have thernmal bridging issues)

Above method is
PIR + Stud sideways + plasterboard= 100 + 38 + 12 = 150mm (100mm of insulation (if none betwene studs) but no thermal bridging issues)

SFK

 

[noseall]

So you think insulated plasterboard is needed to? wouldnt the vapour sheeting deal with the condensation?

No. You need to first understand cold spots and condensation. When a room fills full of moist air (usually when occupied by humas etc), that moisture laden air is hunting for cold spots upon which to condense. It's usually occurs in concealed, low air movement areas behind sofas, or backs of cupboards, or cold zones such as window reveals or ceilings closest to the eaves etc.

Joists and studs can also transmit or bridge the cold from outside to in. So insulating between them wont solve the bridging issue.

 

[hamd01]

To minismise thermal bridging, I would put 100mm PIR on the walls, and then studs to hang the plasterboard, I would put a base plate and top plate on the floor and ceiling and put studs between these. See here for an image:
https://www.carpentry-tips-and-tricks.com/Interior-wall-framing.html
Basically a free standing stud wall infront of your PIR boards.
Then put in cables.
Add another layer of insulation between these studs where there are no cables.
And then normal plasterboard.

It should be noted that this method uses a lot of space.
You were on PIR + Insulated plasterboard = 100 + (25? + 12) = 137mm (125mm of insulation but might have thernmal bridging issues)

Above method is
PIR + Stud sideways + plasterboard= 100 + 38 + 12 = 150mm (100mm of insulation (if none betwene studs) but no thermal bridging issues)

SFK

Understood thanks. The only thing I'm not quite sure with this method is securing the PIR boards to what a slightly uneven old stone wall....not brick or breeze block.

 

[hamd01]

No. You need to first understand cold spots and condensation. When a room fills full of moist air (usually when occupied by humas etc), that moisture laden air is hunting for cold spots upon which to condense. It's usually occurs in concealed, low air movement areas behind sofas, or backs of cupboards, or cold zones such as window reveals or ceilings closest to the eaves etc.

Joists and studs can also transmit or bridge the cold from outside to in. So insulating between them wont solve the bridging issue.

Thanks. What would your solution be?

 

[noseall]

Thanks. What would your solution be?

A secondary layer (across the studs or joists) is essential

50mm across the timbers then fix plasterboards with 100mm screws.