Hello, new user - ceiling insulation query

[Katy]

I’m refurbishing a early 1930s property. Detached. Solid brick wall construction with crittle windows. 

 

Im part way through, structural demolition work complete, 1st fix plumbing done. Electrics 1st fix yet to start. The putting back together has started as the builder has started putting ceilings back together then he will halt till electrician done their work. 

 

I wish I’d found this forum sooner!!!! So many questions and queries I’ve had along the way. 

 

Ive got a question about insulation but hopefully will be able to post on that forum soon specifically 

 

but in the interim here is my query:

 

I am having brand new ceilings put in ground floor hallway and 1st floor bedroom. Above is loft.  

 

It’s a solid wall property with no wall or floor insulation.  Ie high heat loss. Double glazed windows are ordered. 

 

I want to specify insulated plasterboard for new ceilings for thermal performance (not acoustic). 

 

My builder has said most people either just use standard non-insulated plasterboard and then rockwool on top in between the joists.  He thinks I’m going overboard. 

 

My builders alternate suggestion was a standard plasterboard with 1cm foam, (which I think is called a PUR board?) and again rockwool In between joists on top.  Is this effective? 

 

I was thinking PIR board. But then what brand and thickness is appropriate??

 

I just need advice on the most effective material/method for insulating ceilings in intermediate rooms?  Ie bedtooms/lounges from a thermal perspective. 

 

I rang buildbase: 

They said they have 6 different products.  

1) Siniat PIR board at 37.5ml - this is what they recommended as the most effective. 

2) Thermal XP board 27ml

3) 4 different thicknesses of polystyrene (foam) plasterboard at 22, 30, 40 and 50 ml.  

My builder suggests getting this last one at 22ml and that with rockwool in between the joists too will suffice. 

 

He is a youngish builder, early 30s whose forte was the structural work and how I originally appointed him. He’s great to work with, but there are are areas sometimes where I wonder if he’s out his depth or experience. He does listen to my concerns and is willing to work with me But I would really appreciate guidance on appropriate product.  

 

Like I said earlier, he said his previous clients all just used non-insulated standard plasterboard and rockwool between joists at ceilings at ground and 1st floor. 

 

My my concern is this is an old property, very poor thermal performance, i just want to do what’s right for the property. 

 

Im not sure if I’m going overboard or overworrying. 

 

Detached property. The windows I have upgraded from single to double glazed. Wall insulation - external I couldn’t afford!!! Internal I don’t want to lose floor space. Floor is suspended timber non-insulated. Roof insulation I will do and board up as plan to use loft for storage. Ceilings wise - whilst putting up new ones if too far gone during structural work, I want to do right/effective thing thermal wise. 

 

Any insight from those in the know would be appreciated 

 

property is in london.  Building regulations don’t apply as refurbishment of existing property (no extensions). 

 

Photo attached of plasterboard builder suggests 22ml siniat PUR board

 

https://www.siniat.co.uk/en/products-and-systems/products/internal-boards/gtec-eps-thermal-board

 

this is product. Is it right one???

 

many thanks 

 

 

 

Edited August 18, 2019 by Katy
Query added

[Tennentslager]

Welcome @Katy

we like pictures 

and roughly where you are will help with answers due to different regulations for the various nations in the UK ?

[Cpd]

4 hours ago, Tennentslager said:

and roughly where you are will help with answers due to different regulations for the various nations in the UK ?

 

5 hours ago, Katy said:

property is in london.

 

I have just done one of my rooms and put 50mm of kingspan / calotex up below the ceiling and I filled above with 300mm of rock wool. 

The 50mm insulated calotex / kingspan  plasterboard (62mm  including plasterboard face aprox... ) would be my preference as a minimal amount as it’s easy to work with, easy to cut etc. And then as much rock wool above as is feasible.   I think you really need to think about wall insulation, yes you will loose a bit of space but your heating bills will be so much cheaper ! I am putting in 75mm insulated plasterboardon on my walls. I am sure others will be along with advise but your not I over thinking  it, if anything your under thinking it....... you need to insulate the hell out of it unless you want to live in a cold damp house or pay the electric company a shed loads of your hard earned cash every year for the rest of the time your living there.......

[Temp]

The main advantage of foam insulation over rockwool is that foam insulation (PIR, PUR) has a better thermal resistance per mm of thickness. So it makes sense to use foam where thickness is an issue.

 

To my mind the thickness isn't usually an issue in a loft so that would favour rockwool on the floor of a loft rather than foam under it.

 

The exception might be where it's very hard to get a sufficient depth of rockwool at the eaves of a sloping roof (while preserving ventilation above it). In that case a combination seems like a reasonable choice.

 

You may/should also consider adding a vapour barrier to reduce risk of condensation in the loft, especially if the ventilation is inadequate.

 

 

 

[ProDave]

A previous house I owned was a 1930's semi with 9" solid walls.

 

There is no way I could go back to living in a house like that again knowing what I know now about low energy houses and low heating bills.

 

The plasterboard used for the ceiling does not make much difference. You will be adding a LOT of insulation above it won't you, more than the typical 100mm that used to be considered good.  

 

You really should be taking up ALL the floor boards, insulating in between the floor joists and putting the floors back.

 

And really really consider insulating the walls.  Even if you only loose 50mm from each exernal wall to get 50mm of PUR before plasterboarding you will notice a huge difference.

 

And the last point is attention to detail and air tightness.  Nobody is suggesting you try and make it an air tight passive house, but it used to be common in these old houses to leave big holes in the floor with no attempt to seal them so just a place for cold air to get in.

[Declan52]

Standard plasterboard on the ceiling then Rockwool at the depth of the joists, 80/90/100mm. Then roll out a min of 300mm across the joists. Keep your insulated boards for the walls. 

Pay attention to holes in the ceiling for lights as these will need sealed up. 

As Dave points out the gap in between floors will need sorted. As it's an old house the joists will be through the wall do over time gaps will have appeared. Lift the floorboards so you can go round the permiter and seal the wall with a combination of  tape/membrane/motar especially if the gaps are large.

[andyscotland]

To clarify, I think you're asking about the ceilings between e.g. ground and first floor?

 

If so, is your heating zoned - will you be heating rooms downstairs separately to rooms upstairs? If not then there is probably not much value in over-insulating the intermediate ceilings. If the rooms are around the same temperature then not much heat will travel through them and any that does will just reduce the heating demand for the upstairs rooms.

 

The external walls/floors/ceilings are much more of a priority for your money & effort.

[Katy]

Thanks everyone for replies to date.  When I had 1st bought the home, I did go round with insulation experts and they all quoted 25-30 k for EWI (external wall insulation).  Given the price and my budget not being able to stretch that far (I decided not to pursue).  Also my anticipated length of living there is btw 5-10 yrs so had to consider cost effectiveness for me personally. 

 

Yes - the heating has been zoned.  Ground and 1st floor separate.  

 

Upstairs are 4 bedrooms. Here 2 ceilings are brand new - the builder has used standard plasterboard with 12ml foam (ie thinnest PUR board) one can buy and put rockwool between joists.  In the master bedroom which is large - with a big bay window, I have also asked for new ceiling (not yet done) but here I’ve suggested a PIR board (but they are expensive!!!). About 600£ just for the boards for the master bedroom ceiling. This room has 3 external walls as detached and this room is at front.

 

On ground floor - the new ceilings are hallway and kitchen only. So I will insulate here In between the joists with rockwool and insulated plasterboard in hallway only.  The kitchen can’t have insulated plasterboard beneath joists, it will have to between joists (as otherwise affects sliding glass doors which are floor to ceiling. The 2 lounge ceilings have been skimmed.  

 

Reading prior replies - is the collective feedback to lift up all the floorboards on the 1st floor and put rockwool between all joists everywhere?  So that even rooms on ground floor with non-insulated ceilings then are a bit insulated from above?  To reap benefit of zoned heating? 

 

I can maybe look into IWI (internal wall insulation) in the master bedroom (albeit reluctantly). 

 

Ive never done a house refurbishment before, I had no comprehension of what I was inheriting when I bought it.  If only it didn’t have solid walls....

 

like I said, my budget is tight and this isn’t even a forever home (probably btw 5-10yrs).  I currently live in a new build that meets regulations, so I’m sure I’ll feel it, but I just want to do mid-level.  

 

I remember walking round round with a senior builder at the tendering stage, and he seemed to think new double glazing and central heating alone would be fine.  

 

My current builder, also thinks I’ve gone mad and seems to think I’ll be roasting, as about 40% of ceilings will be new with rockwool.  And he said we can insulate the roof properly where 25% heat loss happens. 

 

Thanks 

 

can you clarify - shall I ask the builder to lift all floorboards on 1st floor, to put rockwool btw joists at ceiling of ground floor? The hosts are quite deep here.  If so, does this happen after 1st fix electrical wiring? 

Edited August 18, 2019 by Katy

[ProDave]

What was the EPC rating of the house?  It seems nobody bothers to look, then wonders why it costs so much to heat.

 

And I meant lifting the ground floor boards to insulate the ground floor, that is far more important than inter floor insulation.

[Katy]

Oh thanks for clarifying. I don’t have EPC to hand, but attached is structural surveyors extract 

 

thanks