Insulating Victorian Home

[Venomgrass]

Hello All, Hopefully a kind person will read this and offer me some advise

I'm in the process of reading up about insulating our home which we are renovating. It's a large victorian home solid wall construction with suspended timber floors and a cellar.

I'm considering insulating the external walls using maybe the insulated plasterboard, but I'm worried about the wall thickness exceeding the gorgeous old coving!

Also, I'm planning to insulate the floorboards from the cellar using rockwool 100mm thick, how do you secure this in place? And do I need to cover it with wood, or would some cheaper plastic or something like laminate flooring underlay boards do it?


So many questions, I'm sorry! Any advise recommendation would be greatly appreciated.

 

[Doggit]

Is the property detached or a semi. Do you want to keep the coving, and could you go for External wall insulation, and what's you're budget, and how competent are you.

The rockwool can be help up with chicken wire, or you can staple string to hold it as you go, then use thin battens spaced at about 300mm afterwards to hold it in place.

 

[Venomgrass]

Is the property detached or a semi. Do you want to keep the coving, and could you go for External wall insulation, and what's you're budget, and how competent are you.

The rockwool can be help up with chicken wire, or you can staple string to hold it as you go, then use thin battens spaced at about 300mm afterwards to hold it in place.

Hi, Its huge semi. 3 Stories, very large rooms 7 bedrooms. The outside is rendered and blends in with next door hence me being put off external insulation. Yes I want to keep the coving, please see the below image, this is one side to the house, the building is shaped like an 'L' so larger thn the photo makes out.

Budget, well we have savings but the rest of the home needs a lot of work too. Needs heating, we would love Ground Source HP hence the requirement for decent insulation and changing the windows to double glaze.

Thank You.

 

[motorbiking]

Celotex PL4025 (25mm backed plasterboard will make a big difference to the insulation and probably wont be any thicker if you chip back the plaster back to brick. Tbh, though if I was doing it, I'd go PL4040. I'd mount it with frame fixers to minimise the gap created by dabs. Both will double/tripple the insulation properties of the walls. TBH, the windows are going to be the weak link, so I wouldn't go mad with over specifying the insulation.

For the cellar, you could use 5.5mm non structural hardwood ply, which will be moisture resistant and will cost about £15 a board. Depending on services, you might find a 40-50mm GA4000 board can be wedged in place more easily. Also think about insulating the door

 

[Venomgrass]

Celotex PL4025 (25mm backed plasterboard will make a big difference to the insulation and probably wont be any thicker if you chip back the plaster back to brick. Tbh, though if I was doing it, I'd go PL4040. I'd mount it with frame fixers to minimise the gap created by dabs. Both will double/tripple the insulation properties of the walls. TBH, the windows are going to be the weak link, so I wouldn't go mad with over specifying the insulation.

For the cellar, you could use 5.5mm non structural hardwood ply, which will be moisture resistant and will cost about £15 a board. Depending on services, you might find a 40-50mm GA4000 board can be wedged in place more easily. Also think about insulating the door

Thanks! yes we are in the process of receiving a triple glazing quote.
As for the cellar I'm looking at EARTHWOOL. They do two products, I've linked them below:
+rolled (generally used for loft insulation)
+packed slabs (more rigid for stuffing between rafters/joists)

Which should I buy? My under floor joists are 230mm deep! So should I buy the packed slab which will be easier to fit as they compress and are maximum of 100mm thick. Or the rolled insulation which I can get in 200mm thick and secure with packing tape and a staple gun? I don't understand U or R values so I'm confused which option will give what total U value...

From a bit of research on the calculations, timber floorboards @15mm, R-value=0.16.... so

Rolled Wool @ 200mm
R-value= 4.5 + 0.16 (floorboards)
U-value= 0.2146

Slab Wool @ 100mm
R-value= 2.85 + 0.16 (floorboards)
U-value= 0.3322

so the rolled stuffs better, and cheaper?

Thanks!



Thank You very much, I really appreciate your response.

 

[Doggit]

Thanks! yes we are in the process of receiving a triple glazing quote

The triple glazing we have in this country isn't reckoned to be much better than double glazing, so I'd be inclined to put the extra costs elsewhere.

The rolled stuff is better, simply because it's thicker, but packing tape is not a permanent solution, so I'd look for a polyester type string to use with the staple gun to hold it in place as you go.

You don't need to do all the walls with EWI, but the north and west walls are the most important; which direction does the front of the property face, because if it's south, then you could ignore it.

Motorbikings made some good comments in terms of chipping off the plaster to preserve the coving, but with EWI, you stop the walls getting cold in the first place, so the property warms quicker.

 

[motorbiking]

U value... low number is better

from memory your walls will be somewhere between 1.5 and 2.5. current building regs are around 0.3 depending where you live.

The original part of my home is a 9 inch solid wall on uninsulated floor boards. the first winter was pretty grim.

 

[Venomgrass]

Ohh no... it will be a cold winter here! haha nevermind I have my log burner and a nice supply of wood.

For internal wall insulation, would chipping off the plaster first give me much clearance to prevent masking the beautiful plaster coving with a thicker wall? Or is this asking for trouble.

 

[motorbiking]

drill a small hole and measure how deep before you hit brick.

you've probably got 25mm

make sure you wear protection. it will be full of all sorts of nasties form lime to anthrax laced horse hair.

yeah log burners are ace. amazing how the modern ones extract heat. I've got two with 10 years between them. the newer one puts out twice as much heat

 

[Venomgrass]

drill a small hole and measure how deep before you hit brick.

you've probably got 25mm

make sure you wear protection. it will be full of all sorts of nasties form lime to anthrax laced horse hair.

yeah log burners are ace. amazing how the modern ones extract heat. I've got two with 10 years between them. the newer one puts out twice as much heat

Thank You.
I measured....

Render: 20mm - R-value= 0.03
Solid Brick: 525mm - R-value= 0.63
Plaster: 25mm = R-value= 0.16

So currently@ u-value of ~1.01W/m2K.

The big question now is, do I buy ready insulated plasterboard for the walls, or is it cheaper to buy some kingspan/cellotex insulation boards and buy the plasterboard separate... Any suggestions please?

 

[Doggit]

Whilst it's cheaper to use make up you're own insulated plasterboard, it's no that easy, nor so secure, but if all you've got is 25mm of plaster, then you're not going to get much insulation on the wall before ruining the coving. Kingspan will tell you that the best solution, is to batten the walls with at least 20mm battens, then fix the insulated plasterboard to the battens, and that's going to take you to about 60mm, so 35mm further into the room than at present. You could ignore the battens, but the room wouldn't get so warm.

 

[motorbiking]

I make it 1.3?

PL4025 will take it down to 0.51, PL4040 down to 0.38

If you can't get PL4025 (37.5mm) in as a minimum then I wouldn't bother as any less is going to barely get you U value under 1. Your 525mm solid walls are performing well if your R value is correct. But you'll no doubt have windows with a U value of somewhere between 3 and 6.

Oh and if you have any open fire places, then the rate of air change in the room will be something like 1 hour depending on size. Insulating your walls will make bugger all difference if you have single glazed windows and open chimneys.

If you mechanically fix (toolstation 83958 Phillips Frame Fixing 8 x 80mm ), you'll get very tight fitting, but you will need to check how straight your bricks are as you wont be able to adjust much. Avoid battens.

I think you are looking at costs of around £10-12/m2

 

[Venomgrass]

I make it 1.3?

PL4025 will take it down to 0.51, PL4040 down to 0.38

If you can't get PL4025 (37.5mm) in as a minimum then I wouldn't bother as any less is going to barely get you U value under 1. Your 525mm solid walls are performing well if your R value is correct. But you'll no doubt have windows with a U value of somewhere between 3 and 6.

Oh and if you have any open fire places, then the rate of air change in the room will be something like 1 hour depending on size. Insulating your walls will make bugger all difference if you have single glazed windows and open chimneys.

If you mechanically fix (toolstation 83958 Phillips Frame Fixing 8 x 80mm ), you'll get very tight fitting, but you will need to check how straight your bricks are as you wont be able to adjust much. Avoid battens.

I think you are looking at costs of around £10-12/m2

I might go for the PL4040 or thicker and just accept that modern living means to compromise one wall of each room to insulate the external.
So do I basically just dry fix it to the plaster once wallpaper is stripped? The Cellotex manual says you can also use an adhesive, do I need an air gap?

What do you mean by you make it 1.3?

Thank You.

 

[motorbiking]

I'd take it back to brick if you are going for the 40mm stuff. It will come off fairly quickly with a SDS hammer drill and a blade/spade attachments - I reckon half an hour to an hour per wall. Also gives you an opportunity to add services you might want (electrics, networks, speaker cables etc.) Do double check with an estate agent that you aren't about to destroy highly sought after features.

Glue on plaster is a recipe for it falling off later if it blows.

take it back to brick, maybe dob and dab and then 6-10 no8 100-120mm frame/hammer fixers in each panel through to brick to hold it

1.3 U = 1/sum of R (+ some other bits, which you haven't provided)

 

[Venomgrass]

Hmm so, if I use PL4040, I think my wall u-value will be like, 0.36... Would this be good enough?
I'm in two minds, should I chip away the plaster and then face uneven walls and dot dab method, or stick right onto plaster with fixings and leave the dot and dab off....

Also do these things "need" skimmed, or if I joint filler the seams, fixings can I just paint to save money on a skim coating.

Cheers Motorbiking, your knowledge is really helping my renovation.