Insulation retrofit

kilcul123

Below is my plan and looking to get a bit of advice on whether this is the right solution or not.

Timber frame property built in 1997.

- My plans is to pull out existing plasterboard and fibreglass insulation. Put 50mm PIR board into 80mm stud allowing for an air gap; not sure I can fully fill 80mm stud as air gap will help PIR board reflect heat back? Could be wrong.

-Air tightness tape on all windows, sockets etc.

-Install vapour barrier/air tightness membrane.

-Top up with insulated plasterboard 62.5mm.

Total insulation is 100mm, I know ideally i should be more than 100mm but hoping it will still be a big upgrade from the fibreglass.

TimHorton

https://www.boards.ie/discussion/2058335471/insulation-retrofit

Adding 100mm PIR and improving Airtightness will drastically improve the Thermal Performance and comfort, I have added 100 PIR/Vapour Control and 12.5 MM Foil Backed Plasterboard on the internal walls and the 4 bedrooms that I have done so far and now warm comfortable and easy to heat. My house has double skin block walls with 100mm cavity with 50mm PIR - Getting Cavity filled later this year. I Only insulated the internals of the external walls Thus leaving plenty of Thermal Mass in each room. Biggest Gain came in the 2 Bedrooms at the North facing elevation that each had 2 external walls.

Calahonda52

https://www.boards.ie/discussion/2058335471/insulation-retrofit

TF upgrading is a different animal to cavity walls due to risk of unintended moisture retention in the TF....

whats inside the current pb: plastic sheeting?

are the wall vents properly ducted from (out to in)side

Might be better to augment the GF if it is sagged....

Alu faced PIR is 100% non breathable , especially if you tape the gaps with alu tape across the uprights

What's the purpose of the air gap?

Rather than the 62.5 insulated slab, I would just add the insulation and then do your A/t etc and create a service cavity outside that for sockets, minimises the perforations and cutting out the insulation for sockets is a bit naff

Have you read SI 54/ 2014/2019 which is free from NSAI? registration required as it is then bookmarked to protect the IP but its free

https://shop.standards.ie/en-ie/standards/s-r-54-2014-a1-2019-877610_saig_nsai_nsai_2749895/

Did similar, but we just glued 100mm insulated board. It has foil behind plasterboard layer and foil on back of urethane.

We foamed it onto the existing walls - no gap. Foam all around perimeter of board back to create a air cell between the board and the wall. All seams airtight sealed, including roof to ceiling.

Airtightness tape around all new triple glazed windows.

House loses just 2 degrees over 24hours with an outside temp difference of 10 degrees centigrade.

Success.

kilcul123

So you left the existing plasterboard and insulation in place and topped it up with 100mm insulated plasterboard? Certainly a tidier job than pulling out the existing plasterboard and insulation.

kilcul123

Yeah currently there is a plastic sheet between the PB and existing insulation. We added external vents to allow the frame to breath, very conscious of the problems moisture build up can have on the TF.

From what I have read the air gap allows the PIR foil work more effectively by reflecting heat back in to the room. If there is no air gap this doesn't seem to work as well...though there's probably a good argument to simply maximise the amount of insulation I can fit.

https://www.boards.ie/discussion/comment/121748755#Comment_121748755

Yep that's what we did. We only insulated the external walls. We used mushrooms to hold the board in place for fire safety and whilst the foam glue sets.

Having lived in an old drylined house where I am certain that condensation was going in behind the boards, I paid a lot of attention to airtightness taping. We also have MVHR so the house always has very low humidity.

kilcul123

https://www.boards.ie/discussion/comment/121748805#Comment_121748805

Yours is timber frame also? I'm just going room by room but insulation board straight onto existing plasterboard will make that a lot quicker.

Was looking at retrofitting MVHR in time, not the most straightforward jobs either so that can wait. Thanks for the info

https://www.boards.ie/discussion/comment/121748979#Comment_121748979

Ours is half timber framed, downstairs all block and upstairs studwork.

The boards I used were about a hundred a board. We used 25mm foam backed boards in all reveals.

MVHR was a bitch to install but well worth the effort.