Upgrading Wall insulation on 20 year old house

little_monty

I'm considering options for external wall insulation upgrade which are :

<plaster -100mm block - 40mm cavity - 60 mm insulation - 100mm block - internal plaster>

I haven't calculated the u-value of the walls yet (I don't know conductivity of the insulation) but my goal is to bring house to a decent efficiency (perhaps equivalent to B rating)

(I will also be replacing windows, doors, ceiling insulation, and other work .. I'll also consider getting a 'heat loss' engineer to advise but would like to understand by options better first)

Options as I see them are :

A. Pump the cavity.

Cheapest/easiest option, but I guess it wont give a very significant improvement

Q.1 Any thoughts ?
(anyone knowdo I get conductivity/uvalue of pumped beaded insulation ?)

B. Internal insulation

Medium cost option and should give significant improvement.
But I' concerned about interstitial condensation

Q.2 Is there a limit /or way of calculating the amount of internal insulation without risking condensation ?

Q.3 I've only ever seen Insulated plasterboard fitted directly to walls.. i.e. no battons, air barrier, or waterproof membrane between insulation and wall ..
Is the waterproof membrane in particular important ? (a builder told me No !)

C. External insulation.

High cost option, but should (assumed done correctly) give best results

Q.4 Does the current make up of the wall make EWI suitable for me (e.g. would I need to get walls pumped as well ?

(One concern is cold air from outside would circulate in the air cavity undoing some of benefits of ext insulation ..any thoughts)

Q5. any recommendations for engineer (please pm me)

Any comments in general ?

MicktheMan

little_monty wrote: »

I'm considering options for external wall insulation upgrade which are :

<plaster -100mm block - 40mm cavity - 60 mm insulation - 100mm block - internal plaster>

I haven't calculated the u-value of the walls yet (I don't know conductivity of the insulation) but my goal is to bring house to a decent efficiency (perhaps equivalent to B rating)

(I will also be replacing windows, doors, ceiling insulation, and other work .. I'll also consider getting a 'heat loss' engineer to advise but would like to understand by options better first)

Options as I see them are :

A. Pump the cavity.

Cheapest/easiest option, but I guess it wont give a very significant improvement

Q.1 Any thoughts ?
(anyone knowdo I get conductivity/uvalue of pumped beaded insulation ?)

B. Internal insulation

Medium cost option and should give significant improvement.
But I' concerned about interstitial condensation

Q.2 Is there a limit /or way of calculating the amount of internal insulation without risking condensation ?

Q.3 I've only ever seen Insulated plasterboard fitted directly to walls.. i.e. no battons, air barrier, or waterproof membrane between insulation and wall ..
Is the waterproof membrane in particular important ? (a builder told me No !)

C. External insulation.

High cost option, but should (assumed done correctly) give best results

Q.4 Does the current make up of the wall make EWI suitable for me (e.g. would I need to get walls pumped as well ?

(One concern is cold air from outside would circulate in the air cavity undoing some of benefits of ext insulation ..any thoughts)

Q5. any recommendations for engineer (please pm me)

Any comments in general ?

How long have you lived in the house and how does it "perform", i.e why are you considering an energy upgrade? This may seem a strange question but very often people concentrate on the wrong thing such as improving the insulation when in fact lack of air tightness is the real culprit. So with that in mind, have you considered having a full heat loss survey done (which not only looks at insulation values but also airtightness, ventilation, ch distribution and control).

You have a cavity wall construction so the following should be taken into account:

Pumping the residual cavity can be done but depending on the construction technique over the opes can leave significant thermal bridging (think condensation / mould as well as heat loss). If EWI is being considered, then pumping the cavity is a must, otherwise ewi is ineffectual.

You are correct to be concerned about interstitial condensation with internal insulation. You can model the risk with wufi but personally I wouldn't consider internal insulation for several reasons especially if you have other options.

If ewi is done correctly (e.g. from footings to up past the soffit meeting the ceiling insulation, the insulation boards/batts buttered to prevent thermal looping etc) then this is the superior option (and if you are replacing the windows then you have the opportunity to move the new windows out such that the frames are wrapped in the ewi as well, thus eliminating thermal bridging here and giving you a nice deep window board internally). Also, there can be (relatively) little cost difference with increasing the insulation thickness thus improving the wall u-value further.

But as I alluded to at the top, make sure that you are fully aware of the main heat loss mechanism(s) before spending on any particular measure.

little_monty

Thanks for your very informative post MickTheMan

Some answers to your questions and further thoughts below :

- I haven't lived in the house. I'm just sale agreed.

I'm just doing my own early research now before I complete sale at which stage I can get builder/engineers to look further.
(Can anyone recommend a 'Heat Loss' Surveyor in west dublin/north kildare area ?)

The house does need new windows and other refurbishment work. So now is the time to consider the wall insulation which I agree should be considered together with roof, windows, air tightness, ventilation etc

- Interesting what you say that EWI needs air cavity to be filled. This makes sense.
(its something to check when getting EWI quotes along with other points you raise about doing EWI correctly).

- I wonder would most EWI companies actually pump walls where air cavity exists ?

- When you say pumping walls mightn't be useful .. you are referring to pumping walls without EWI .. ie pumping walls should be possible and useful IF getting EWI

- Interesting also what you say about Internal wall insulation. Can you comment further how it should be done correctly (or how not to do it)?

MicktheMan

little_monty wrote: »

1. I'm just doing my own early research now before I complete sale at which stage I can get builder/engineers to look further.
(Can anyone recommend a 'Heat Loss' Surveyor in west dublin/north kildare area ?)

2.The house does need new windows and other refurbishment work. So now is the time to consider the wall insulation which I agree should be considered together with roof, windows, air tightness, ventilation etc

3.- I wonder would most EWI companies actually pump walls where air cavity exists ?

4.- When you say pumping walls mightn't be useful .. you are referring to pumping walls without EWI .. ie pumping walls should be possible and useful IF getting EWI

5.- Interesting also what you say about Internal wall insulation. Can you comment further how it should be done correctly (or how not to do it)?

1.Yes. PM me for details
2. First get the best advice you can. It may be that to do it "right" is cost prohibitive now so whatever you have done ensure it doesn't rule out the better option in the future. For example, if EWI is out of reach now, you can always have the cavity pumped now and do the EWI at a later date.
3. I have come across some cases where EWI was applied without pumping the walls, so beware of the BS from some contractors.
4. I'm not sure what you're asking here. Pumping the cavity (CWI) may or may not deliver energy saving / thermal comfort. It depends on a number of factors and can really only be discerned with a full heat loss survey.
5. If you have the option to either do CWI or EWI then I wouldn't even think about Internal wall insulation. There have been many discussions over the years here in the C&P forum on this subject. Perhaps a search will inform you better.

little_monty

Just to give my latest thoughts on the wall insulation (in advance of full heat loss survey)

- Cavity wall with ~100mm combination of Existing aeroboard and new pumped insulation (assuming its feasible) should give a u-value approx. 0.3 (this sound reasonable ?)

- EWI can bring uvalue below 0.2 .. but I don't think the cost / benefit is worth it for now ..

However I would like to keep this option open for the future !

- This will allow better investment in windows/ air tightness / ventilation / attic insulation / heating

I'm just wondering now how high a spec I should go with windows assuming walls with u-value 0.3 currently .. but possibly <0.2 later ?

Also its recommended the windows should be 'moved out' if eventually I externally insulate .. I wonder how important this is .. and if it will be feasible / good idea to move windows ?

MicktheMan

little_monty wrote: »

1.- Cavity wall with ~100mm combination of Existing aeroboard and new pumped insulation (assuming its feasible) should give a u-value approx. 0.3 (this sound reasonable ?)

2- EWI can bring uvalue below 0.2 .. but I don't think the cost / benefit is worth it for now ..

3.However I would like to keep this option open for the future !

4. I'm just wondering now how high a spec I should go with windows assuming walls with u-value 0.3 currently .. but possibly <0.2 later ?

5.Also its recommended the windows should be 'moved out' if eventually I externally insulate .. I wonder how important this is .. and if it will be feasible / good idea to move windows ?

1. on paper yes, 0.3 is reasonable but in reality you could double or treble this - reason: the chances are that the current insulation board isn't installed correctly (i.e. tight against a clean inner leaf and tightly abutted to each other) and pumping with a bonded bead product won't fix this.
2. Comes back to what is the main heat loss mechanism
3. Good
4. As good as you can afford (the windows will always be the weakest element for conduction heat loss.
5. This is a very important detail with ewi. It eliminates the thermal bridging if done properly. The more you insulate a house, the more important thermal bridging becomes from heat loss but also from condensation/damp point of view. If you upgrade your windows now to the best your budget allows, these windows can always be moved out later when installing the ewi.

BryanF

Ewi give a better uvakue than .2wm2k especially if the cavity is pumped first.

little_monty

thanks for the comments guys ..

Good point on possibility of the insulating board not being installed 'tightly' against inner leaf ..
Hopefully in my case its not so badly installed and some benefit at least can be gained from pumping.

Its good news i should be able to move windows out if i go for EWI at later date.

I'll spend my budget now on pumping along with on windows/attic insul/air tightness/ ventillation/Heating .. ill know after couple of years if i need to go with EWI