Thermal insulation plasterboard & heat loss

Rippone

Hi everyone,

I recently installed Thermal insulation plasterboards inside across external walls .

Below is the product the builder recommended to install

https://www.travisperkins.co.uk/thermal-insulated-plasterboard/british-gypsum-gyproc-thermaline-pir-tapered-edge-insulated-plasterboard-2400mm-x-1200mm-x-38mm/p/383834

38mm thick. Thermal Conductivity 0.022 W/mK

I am top floor (3rd floor). With 3 external walls (meaning South, East, West sides of my property are exposed to the outside). Double glazed windows. 100mm glass mineral wool loft insulation.

I am experiencing what I would believe to be a quite significant heat loss. E.g. in the last 2 nights I switched the heating off in the living room at around 10/11pm and by 7am and the temperature dropped from 18.5 degrees to 12.5 degrees. (temperature has been roughly +4/-1)

Roughly using 22 kWh per day (55m2 flat) of just electricity for the radiators (yes I am in a electricity only flat, I know, stupid choice).

I believe the building may have cavity walls (built in 1990), but no cavity walls insulation. Property management is ignoring my requests to have cavity walls insulated. 

Was the type of plasterboard I installed not the right choice? What else I can do to help with this heating loss (in a way that is cost effective)?

Any advice?

FreeBear

Rippone said: Was the type of plasterboard I installed not the right choice? What else I can do to help with this heating loss (in a way that is cost effective)?

The type of plasterboard is about the best you can get in terms on money-v-performance. 63mm or even 78mm would have been better (both would hit the current recommended u-value for refurbishment). But to replace or add to what you already have is not cost effective. Adding another 200mm to the loft insulation will cost relatively little and help to reduce the heat loss slightly.

heavy thermal line curtains are another low cost measure - Just make sure they are tucked behind any radiators mounted under windows. On the subject of windows - Check that you are not getting any draughts coming in around the edges.

ComicGeek

What was it like before you installed the insulated plasterboard? A 6 degree drop in internal temperature is not abnormal, and the insulated plasterboard will have helped - it only slows down the heat lost to outside, it doesn't stop it.

stuart45

It should raise the air temperature quicker now, and use less energy to keep it there, but when you have external, or cavity wall insulation, the masonry holds the heat for longer in a similar way to bricks in an electric storage heater.

Rippone

FreeBear said:

Rippone said: Was the type of plasterboard I installed not the right choice? What else I can do to help with this heating loss (in a way that is cost effective)?

The type of plasterboard is about the best you can get in terms on money-v-performance. 63mm or even 78mm would have been better (both would hit the current recommended u-value for refurbishment). But to replace or add to what you already have is not cost effective. Adding another 200mm to the loft insulation will cost relatively little and help to reduce the heat loss slightly.

heavy thermal line curtains are another low cost measure - Just make sure they are tucked behind any radiators mounted under windows. On the subject of windows - Check that you are not getting any draughts coming in around the edges.

Thank you!

I am extremely upset with myself as I should have insisted to have the 63mm installed instead. Which it is something I had discussed with the builder, but for whatever reason he insisted that 38mm was enough / and he confused me with his explanation. I am now wondering how much of a difference would have made. 

Yes, I thought about the thermal line curtains, which I will mount in the windows recess. Right now, I have no curtains as I am doing some redecoration works.

I am considering adding an extra 200mm to the loft. Although, I have been quoted a £600 and I have been told I won't really recuperate the costs in the medium term and it is not really worth it. Maybe I will do it myself, saving labour money, just worried I have little DIY experience. 

ComicGeek said:

What was it like before you installed the insulated plasterboard? A 6 degree drop in internal temperature is not abnormal, and the insulated plasterboard will have helped - it only slows down the heat lost to outside, it doesn't stop it.

stuart45 said:

It should raise the air temperature quicker now, and use less energy to keep it there, but when you have external, or cavity wall insulation, the masonry holds the heat for longer in a similar way to bricks in an electric storage heater.

I think adding the plasterboard has made the place feeling slightly warmer overall / walls feel less colder. It's difficult to compare with last winter. It was my first winter in this place, and I was in and out the country for family issues. Feels now that the heat is kept longer and it's cozy when the temperature is mildly cold, as it was until 1 week ago in London. But now that it is proper winter cold, I would have expected a slower heat loss because of the plasterboard. 

chris_n

While 63 mm would be twice the insulation thickness it is no where near twice as effective, it is always diminishing returns with insulation. Perhaps the easiest/cheapest next step is to apply window film where practical. Even though your windows are double glazed the internal glass is still cold, fitting film reduces that. People often say the film is noisy, this is only true if there is a draught coming in. If that is the case then fixing the draught gives a double bonus.

FreeBear

Rippone said: I am considering adding an extra 200mm to the loft. Although, I have been quoted a £600 and I have been told I won't really recuperate the costs in the medium term and it is not really worth it. Maybe I will do it myself, saving labour money, just worried I have little DIY experience.

if you are reasonably fit & able, putting down loft insulation does not require any great skill. Just unroll the stuff at 90 degrees to what ever is already down. You may need some short lengths of planks to put across the joists as you work, and don't forget to use a dust mask and a pair of marigolds.

ThisIsWeird

FreeBear said:

Rippone said: I am considering adding an extra 200mm to the loft. Although, I have been quoted a £600 and I have been told I won't really recuperate the costs in the medium term and it is not really worth it. Maybe I will do it myself, saving labour money, just worried I have little DIY experience.

if you are reasonably fit & able, putting down loft insulation does not require any great skill. Just unroll the stuff at 90 degrees to what ever is already down. You may need some short lengths of planks to put across the joists as you work, and don't forget to use a dust mask and a pair of marigolds.

And take care to not seal up the eaves and prevent the required through-flow of ventilation to keep the loft area dry.

If in doubt, post some photos of what it's like up there, espec where the roof meets the walls.

ThisIsWeird

Hi Rippone.

Yes, it's a shame you didn't go thicker while you were at it - the only reasons not to are the additional cost (relatively little), and the loss of floor space inside the room (ditto). So your builder did you no favours.

However, what Chris says above it correct - it's a law of diminishing returns! Twice the thickness will likely only present a tenth of an improvement - obviously crude guestimates plucked out of the air, but if you imagine the 1" of PIR on your existing boards improving the wall's insulation value tenfold, then it follows that an additional inch will only improve this further by a tenth of a tenth!

I have said this before, but I'll say it again for you - I am sitting in a room that used to be an attached garage with a single-skin block wall. This has 1" of Jablite (expanded polystyrene insulation - cheap and nowhere near the best U value) followed by exactly what you have - 38mm TIP (or TLB). I did this very deliberately, as the 'garage' is narrow - only 8' wide - but it is still the easiest room in my house to heat! In fact, the ol' plasma TV I used as a PC monitor would do the job - 200 watts of otherwise waste!

The main reason why this room is easier to heat than the rest of my '30s house is because it has a solid floor, so zero draughts. (On this concrete floor I added Jablite again, ranging from only 1", to around 4+" as the floor sloped. Ie - next to no insulation. BUT, it's perfectly good, with the pine T&G boards on top.)

Sooo, what I'm getting to is - cut off any draughts.

The two downstairs bedrooms - carpets on the original T&G floorboards over a draughty void - are much much harder to heat, simply because they are 'draughty'. I know that they are, because they have new DG fitted, but if I close the door I can still feel the draught coming into the rest of the house from them...

Soooooo, the next step - apart from adding to the loft insulation (cheap and cost-effective if you can DIY it, and almost certainly you can...) - is to stop the draughts.

Do you find that the rooms take longer to get up to temp if it's breezy outside, rather than just 'cold'? If you close the door to this room, can you still feel a draught coming out (or in) under the door? Try a match or lighter flame. That is heat literally being drawn away.

The insulated board you've added to your walls should have made a HUGE difference, and extra thickness above this - whilst it would have helped, but wouldn't necessarily have transformed - is unlikely to have been transformative, so now look at other potential issues - loft/ceiling insulation, and - especially - draught proofing.

Rippone

ThisIsWeird said:

....

Thank you so much for your insight! Will definitely look at draught proofing the apartment!

ThisIsWeird

Floors, and especially around the room perimeter under the skirting boards