Insulating a pebble-dash semi

Qualitymark

Is it possible to insulate a pebble-dashed semi-detached house, and roughly what should it cost for a typical three-bed semi in Dublin (two external walls - the front is impossible because it has brick halfway up).

By the way, this isn't a cavity wall - it's a 1930s house, so it's concrete with pebble-dash laid on top.

Carlow52

yes but doing 2 sides only is a waste of time, money etc

Qualitymark

Sorry, meant three sides!

Actually, I now realise I'm not sure if it's a cavity wall or not. Don't know how to find out.

Carlow52

Qualitymark wrote: »

Sorry, meant three sides!

Actually, I now realise I'm not sure if it's a cavity wall or not. Don't know how to find out.

why cant u 'do' the brick?

re what u have: ask ur neighbour, wall thickness can be a clue, else take off a wall vent
or
{ put an imitation ATM on the wall and some skobe with a jcb will dig it out}

Qualitymark

The brick's kind of nice; I wouldn't like to cover it up.

Carlow52

Qualitymark wrote: »

The brick's kind of nice; I wouldn't like to cover it up.

Well then the EWI will the equivalent to going topless.

In addition u wont get a grant if its a topless job

Qualitymark

Bottomless, really. But I don't think I'd be allowed to change the look of the house substantively.

championc

If you have a Cavity Block wall or s solid concrete wall, you're always better to insulate on the inside. I found the following document when trying to decide what was best for my house - http://www.josephlittlearchitects.com/documents/hollow%20block%20wall%20assessment_BLC_260609.pdf

You can see that external insulation allows for your house to heat your walls up !!. I want to heat inside the house, not the physical house please. In addition, from their findings (on page 8), it would seem that 38mm of internal insulation is better than 100mm of external.

I ended up just doing the hall, stair and landing gable wall. Plasterboard was about 200 and then another 250 to have the whole wall re-plastered. So this will repay itself a darn side quicker than the external job me thinks.

MicktheMan

championc wrote: »

If you have a Cavity Block wall or s solid concrete wall, you're always better to insulate on the inside. I found the following document when trying to decide what was best for my house - http://www.josephlittlearchitects.com/documents/hollow%20block%20wall%20assessment_BLC_260609.pdf

You can see that external insulation allows for your house to heat your walls up !!. I want to heat inside the house, not the physical house please. In addition, from their findings (on page 8), it would seem that 38mm of internal insulation is better than 100mm of external.

I ended up just doing the hall, stair and landing gable wall. Plasterboard was about 200 and then another 250 to have the whole wall re-plastered. So this will repay itself a darn side quicker than the external job me thinks.

How do you come to this conclusion? Imo, it is completely at odds to what J Little concludes in his various published studies as well as building physics.

championc

Doh, keep the heat inside the house rather than allowing ANY of it to enter walls at all

BryanF

championc wrote: »

If you have a Cavity Block wall or s solid concrete wall, you're always better to insulate on the inside.

:eek: thats the greatest load of sh.. ive seen on here in along time

I found the following document when trying to decide what was best for my house - http://www.josephlittlearchitects.com/documents/hollow%20block%20wall%20assessment_BLC_260609.pdf
You can see that external insulation allows for your house to heat your walls up !!. I want to heat inside the house, not the physical house please.
In addition, from their findings (on page 8), it would seem that 38mm of internal insulation is better than 100mm of external.

[/QUOTE]

from page 6: you've missed something important in your assessment of this study;)

Buildup (listed from inside):
Internal surface resistance
15 mm plasterboard, on
38 mm sheep wool ( = 0.04 W/mK) between timber battens, on
80 mm wood fibre board ( = 0.04 W/mK), on
15 mm plaster, on
215 mm concrete hollow block (40 + 135 + 40) with air layer horizontal heat flow, on
20 mm external rendering (cement/sand)
External surface resistance

go have another read

Qualitymark

Surely @championc is correct:

3.2
Existing wall cavities filled with insulation
This condition represents the discredited practice of filling the cavities in the hollow block wall. No other changes are made to the original wall.
The numerical analysis proves that filling these cavities gives a substantially smaller reduction to the U-value of the original wall (~33%) than suggested by the ‘Combined Method’ (as set out in TGD L Appendix A 2.2). When used the latter methodology gives a reduction of ~50% from the U-value of the original wall, which we can prove is an over- estimation of the value of filling the cavities of 52%. See Figure 7 for comparison of the calculated U-value with that approximated under the ‘Combined Method’. Please also see Construct Ireland magazine (Issues 6 & 7, Vol. 4, published February & May 2009) for additional information on problems associated with filling cavities of hollow block walls.

BryanF

Qualitymark wrote: »

Surely @championc is correct:

about what?? you've haven't even sniffed at how this could be plausible in the text you've quoted.

there's no point in insulating cavity blocks - that's cavity blocks!! stated as

filling the cavities in the hollow block wall

this it taken as a given!! everyone knows this, you either insulate internally or externally

championc states

If you have a Cavity Block wall or s solid concrete wall, you're always better to insulate on the inside.....In addition, from their findings (on page 8), it would seem that 38mm of internal insulation is better than 100mm of external.

this is blatantly incorrect and a total misrepresentation of the study he is quoting.. he has neglected to note that there is 80mm of wood fibre board in the study s calculation, on top of the 38mm which Championc is suggesting (i have highlighted in bold this in the post above). the wood fibre has a similar conductivity of (for example) rockwool..

Qualitymark

BryanF wrote: »

there's no point in insulating cavity blocks - that's cavity blocks!! stated as

this it taken as a given!! everyone knows this

Does everyone? I'm a bit startled by this - what is cavity wall insulation if not insulating cavity blocks?

BryanF

hollow block also known as cavity block


cavity wall which SHOULD be insulated

Qualitymark

Hm. Thanks @BryanF. Now all I have to do is find a competent and honest person who can look at the possibility of insulating the house, and tell me if the walls are cavity or not.

championc

BryanF wrote: »

championc states

this is blatantly incorrect and a total misrepresentation of the study he is quoting.. he has neglected to note that there is 80mm of wood fibre board in the study s calculation, on top of the 38mm which Championc is suggesting (i have highlighted in bold this in the post above). the wood fibre has a similar conductivity of (for example) rockwool..

Yes, I see it now and I apologise. However, can you then just clear up one single point for me.

Is it better to allow your house heat into your walls or not ? I read somewhere too that with cavity blocks, you can have a sort of drafting effect through the columns since obviously, the use of cavity blocks was done at a time when nobody had any insulation in mind at all - and attic insulation was, at best 2" deep !!

For Qualitymark, a cavity is a space between an interior and exterior wall. A cavity block is like this.

championc

Qualitymark wrote: »

Hm. Thanks @BryanF. Now all I have to do is find a competent and honest person who can look at the possibility of insulating the house, and tell me if the walls are cavity or not.

If you know the year of build of the house (and maybe location), some experts on here might be able to give you a pretty good idea

Qualitymark

1930s, and I even know the builder, Hughes, but haven't been able to track down any information about said Hughes, apart from the fact that they built these houses as a tiny estate, with about four different models of house - some with porches, some with arched doorways, some with full bay windows and some half-bays, and so on.

BryanF

re: drafting effect through the columns

cap the blocks at roof level sealing the air that's inside them, while doing this it would be a great time add adequate insulation where the roof meets the wall

wiskyjack

sorry to necro the thread.

but im in a simular position to the OP. i have a 1970 semi D 4 bed with a converted garage on the side. the walls are all hollow block ( single course no cavity) with plaster external (pebble dash) & internal, and no insulation.

some days it feels colder inside than outside.

what would be the best option of external insulation??

BryanF

wiskyjack wrote: »

sorry to necro the thread.

but im in a simular position to the OP. i have a 1970 semi D 4 bed with a converted garage on the side. the walls are all hollow block ( single course no cavity) with plaster external (pebble dash) & internal, and no insulation.

some days it feels colder inside than outside.

what would be the best option of external insulation??

External insulation, assuming you have enough space to plaster afterwards

Qualitymark

A fellow came along and looked at my place, lifted the lip, picked at the wall and said it couldn't be done because it was brick to the hip so would be a protected structure, and even if it could be done, external insulation on a 3-bed semi pebbledash would be €13,000. We've put on an extra jumper and enjoy playing the game of Whose Breath Is Steamier.

wiskyjack

Qualitymark wrote: »

on a 3-bed semi pebbledash would be €13,000.

good to know,

Qualitymark wrote: »

We've put on an extra jumper and enjoy playing the game of Whose Breath Is Steamier.

i know the feeling, i flushed out the water in the heating system, it was more metal than water. that alone was worth it as the clean water heats up faster. also replaced a few rads.

the main issue is the box room. its on the gable end and over the hall to boot, so its the coldest room in the house.

im in the middle of topping up the attic insulation.

Qualitymark

wiskyjack wrote: »

i know the feeling, i flushed out the water in the heating system, it was more metal than water. that alone was worth it as the clean water heats up faster. also replaced a few rads.

Ah yes, central heating. The trouble is that the gas is now so dear that central heating is no longer something you use routinely. It only gets turned on here on very cold days, for half an hour or an hour here and there.

the main issue is the box room. its on the gable end and over the hall to boot, so its the coldest room in the house.

The same here, but in this house it's the cold northeast-facing side wall. I asked about the possibility of insulating only this (externally), and was told it would be pointless. Insulating it internally might work, I suppose, but it would take three inches off the width of the stairs.

Maudi

Qualitymark wrote: »

Ah yes, central heating. The trouble is that the gas is now so dear that central heating is no longer something you use routinely. It only gets turned on here on very cold days, for half an hour or an hour here and there.



The same here, but in this house it's the cold northeast-facing side wall. I asked about the possibility of insulating only this (externally), and was told it would be pointless. Insulating it internally might work, I suppose, but it would take three inches off the width of the stairs.

Whats on the stairs wall at the minute? Sand/cement skim or plaster board?

Qualitymark

Maudi wrote: »

Whats on the stairs wall at the minute? Sand/cement skim or plaster board?

On the outside, pebble-dash and a garage; on the inside, the original plaster from the 1930s. I'm now vaguely wondering how much it would cost to get internal insulation (and how to find someone competent to do this job, which apparently can cause sick building syndrome if it's not done properly - I have asthma, and mould is bad news).

dathi

Qualitymark wrote: »

I suppose, but it would take three inches off the width of the stairs.

be careful here, to comply with building regs stairs must be 800mm wide

murphaph

Do they physically remove the pebble dash on such houses or plaster over it before applying external insulation?