Hello & Cavity wall insulation

[Strangey71]

Hi

I just wanted to introduce myself and ask a question. I was originally a gas engineer started with BG as an apprentice back in 1987, I have worked in the building /property industry ever since I now have my own property management company so if I can help out on any queries I will. I have my first question, I recently moved to a conservation area, my property comes under article 4 but where we are is split into 2 tiers and ours is the lesser tier so I can make alterations to the property within reason but need to keep the character of the area. Hardly any work as been done on the property since it was built except for 2 badly built extensions that need tidying up, My question is my first job now I have made the building watertight is insulation, I have 4"cavity walls which I will get insulated but is there a preferred insulation for cavity walls and would I benefit greatly from exterior insulation (would exterior insulation be worth it?) I have to repair and decorate the exterior anyway but don't want to go to the expense of exterior insulation if it's not worth it. the property is detached.

[Redbeard]

Hello!

 

Can we assume that the exg masonry is rendered? 

[Jilly]

Hello! You might find you need planning permission for external wall insulation (EWI) as it will have to go under something, which will change the appearance. All of the window reveals would need adjusting. 
Cavity wall insulation would be ok, with caveats. Someone will be along to advise as I only have experience of 1970s retrofit which caused damp. 

[saveasteading]

44 minutes ago, Jilly said:

window reveals would need adjusting. 

then there is how it interfaces at the eaves.

[Redbeard]

4 hours ago, Strangey71 said:

I have 4"cavity walls

I had originally taken that as 'walls with a 4" cavity'. I suppose it could also mean ' 2 skins of 4(and a bit?) inch brickwork, with a cavity (width unspecified)'. What age is the house? I don't *think* I have ever come across a 4" unfilled cavity. They tend to be around 2" or even less. (I accept that anomalies exist.

If you do have a 4" cavity then with graphite EPS bonded beads blown in you could possibly achieve a U value (unadjusted for (e.g) bridging at cavity closures etc.) of under 0.27W/m2K, which is none too shabby.

[Strangey71]

13.5" Wall, exterior walls including plaster on the inside and render on the outside, I assumed 2 walls of 4" wide bricks and 1.5" for the plaster and render and bobs your uncle, cavities are normally between 100mm to 150mm, on a 1950's built house there not always perfect so I was edging on the side of smaller to see the numbers. I haven't actually knocked one open yet so it may all change at that moment. Would you think I would benefit greatly from outside insulation after cavity wall insulation I don't think so. Want to try and be as green/environmentally friendly as my budget will allow really

Edited April 3 by Strangey71

[Iceverge]

That kind of cavity with EPS blown beads would be fine.

 

Like muted above I'd be surprised if that was actually the case however. I suspect you'll get a 2" or 50mm cavity. 

 

It'd be still worth doing however. U value 0.66 W/m2K. 

 

Technically external wall insulation (EWI) is a great solution thermally. It keeps the whole structure warm. You have a really safe install in terms of moisture buildup and the associated problems. 

 

However the renders are expensive, you may need to alter the roof and it isn't as robust as a sand and cement finish. 

 

Couple of questions.

 

1. Do you have any pictures to share? 

2. Are you redoing the interior anyway? 

3. Will it require re wiring/plumbing etc? 

4. Can you access an SDS drill and make a small hole to see how deep the cavity is? 

 

 

 

 

 

 

[Strangey71]

Hi 

1, Yes I can attach photos, no problem.

2, We are redoing all the interior, but some rooms don't have space to add internal insulation

3, Yes I will rewire the whole house and 90% of the plumbing

4, I can do that closer to start of main works.

5, I will have to get the exterior patched up and painted anyway by the end of the job. cracks filled and smartened and painted I will carry out but the outside insulation will be done by a contractor.

I just wanted to know, as most insulation gains are gained from the first part of insulating and after that the gains decrease, wether once I had insulated the cavity, all be it if it's only 50mm would I really benefit from exterior insulation.

[Strangey71]

[Strangey71]

Front and back pretty much identical, the depth of property is 6m deep, going to have new front door but windows will stay.

 

[Iceverge]

Pics paint a thousand words thanks. 

 

The exterior looks pretty smart. 

 

There isn't much existing exterior overhangs so EWI would be more awkward. 

 

EPS beads and closed cell polyurethane foam are your choices for the cavity fill although the latter is 4 times the price. 

 

If you can I'd drill a hole now. It only needs to be 5mm though one leaf. You could patch it with a piece of chewing gum! It will inform your decisions early. 

 

 

Regardless of the insulation there are much bigger gains to be had form airtighness and MVHR/mechanics ventilation.  Have you though about any tactica to deal with these? 

 

 

[Strangey71]

Good morning Iceverge, yes I have. I have been involved in small refurbs where MVHR has been installed and various heat recovery units have been used and they worked amazingly well to combat damp and even made the properties feel warmer, but they were flats, I am told that if you can’t get the property sealed and pressure tested it’s  not worth it. I think getting this 1950 built house to the level required would be almost impossible.

i am open and willing to look into every single suggestion, I have even looked into waste water heat recovery units.

i just want to see a decent return and improvement. I keep looking at Air source heat pumps but I have spoken to quite a few people with experience in them and it’s all disappointing! Seems they only work if you keep your boiler as back up, then you don’t get the grant. Please send me a list and I’ll research it all.

[joe90]

You have not mentioned extra insulation In the Roof and floor areas, it all adds up!

[IGP]

I’ve got EPS beads in my 1928 semi detached, 65mm cavity and can highly recommend. 
 

Not only is it warmer, it’s quieter too! 

[Iceverge]

It depends. 

 

Assuming you're  redecorating the inside too? Can you dig out the floors. 

 

It's very possible to get excellent airtighess on a room by room basis. 

 

For some reason everyone looks at MVHR only through the lens of money saving. This neglects the health and comfort benefits. Have a read of one of the many threads on here and you'll get a flavour of the benefits/drawbacks. 

 

Likewise with ASHPs in retrofits. There seems to be a new thread monthly where the whole thing gets thrashed out again. 

 

 

[Strangey71]

Yes, As for MVRH's I understand the ' only through the lens of  money ' and I think they are worth it for damp prevention and generally better feel to the atmosphere in the property, and you are pushing an open door but I read unless the house is airtight don't bother, if you think otherwise I would be interested to know.

As for ASHP's I have come to the conclusion of they are ok! Should be called 'ELECTRIC' Air source heat pumps because no one ever seems to get the running costs they were promised by the designer, they aren't any good if you need to place the fan unit anywhere near a neighbours house and they really need a boiler for back up when the weather gets colder. I spoke to someone who had UFH throughout downstairs and he said at best he would call it, low background ambience not heating the room, but I did ask if he left it on permanently like they advise and he kinda fudged the answer.

Soo at this moment I think yes definitely to EPS beads cavity wall insulation (upon further investigation) 

Yes definitely to MVRH and like you said take it on a room by room basis.

Any other ideas I am all ears or eyes as it's an internet forum.

5 hours ago, joe90 said:

You have not mentioned extra insulation In the Roof and floor areas, it all adds up!

I have inherited 300mm loft insulation but I think I will insulate between roof rafters as well and definitely insulate with floor with PIR, I have 4"joists on the ground floor and I will have a company we have used before advise me on that underfloor insulation but will probably be 50mm PIR boar and then 50mm their pipe trays with 50mm insulation which gives me 100mm on ground floor.

[Jilly]

Steamy Tea will tell you that might well not be enough insulation under the ufh. A lot of people here have put an electric Willis heater or two as a back up to a ASHP, rather than a boiler. 

[Canski]

On 01/04/2024 at 16:54, saveasteading said:

then there is how it interfaces at the eaves.

not to mention the verges

Edited April 5 by Canski

[Strangey71]

21 hours ago, Jilly said:

Steamy Tea will tell you that might well not be enough insulation under the ufh. A lot of people here have put an electric Willis heater or two as a back up to a ASHP, rather than a boiler. 

To tell you the truth when you do the maths on ASHP they really really don't stack up, thy'll only really be worth it if gas prices soar and electricity comes down a lot, I am looking into Solar Panels though so that may be game changer, but those added costs for that even when I take everything at best case don't stack up, for cost, comfort, usability or maintenance. It's a shame really because the best outcome after all the insulation would be a hybrid system of ASHP and Combi boiler but government say no.

[Jilly]

If you have an uber insulated and airtight house with MHRV it should use very little energy, whatever method you chose.

[joe90]

2 hours ago, Strangey71 said:

To tell you the truth when you do the maths on ASHP they really really don't stack up, thy'll only really be worth it if gas prices soar and electricity comes down a lot,

I disagree, with gas prices a third of electricity and ASHP generally having a COP of 3 or better they are comparable.

2 hours ago, Strangey71 said:

I am looking into Solar Panels though so that may be game changer,

Yes, you can self generate electricity but cannot generate gas.

2 hours ago, Strangey71 said:

when I take everything at best case don't stack up, for cost, comfort, usability or maintenance. It's a shame really because the best outcome after all the insulation would be a hybrid system of ASHP and Combi boiler but government say no.

Costs for an ASHP are coming down quickly, why should an ASHP not give the comfort ? (Mine did)  Usability, why?   An 
ASHP needs lass maintenance than a combi (and no standing charge for gas supply),  

[IGP]

2 hours ago, Strangey71 said:

To tell you the truth when you do the maths on ASHP they really really don't stack up, thy'll only really be worth it if gas prices soar and electricity comes down a lot, I am looking into Solar Panels though so that may be game changer, but those added costs for that even when I take everything at best case don't stack up, for cost, comfort, usability or maintenance. It's a shame really because the best outcome after all the insulation would be a hybrid system of ASHP and Combi boiler but government say no.

I’d say that’s not quite right. 
 

check out https://heatpumpmonitor.org and quite a lot of systems pushing 4+ SCoP easy. 

[Iceverge]

On 05/04/2024 at 14:42, Strangey71 said:

I read unless the house is airtight don't bother, if you think otherwise I would be interested to know.

 

You could easily get to 2-3 ACH50 with care. In any case airtighess makes no difference on a calm day. Without mechanical ventilation or a strong stack effect (heating on and windows open) your house will be stuffy.

 

My advice is to stay away from ASHPs in your case. A gas boiler will fit your expectations much closer. 

 

Regarding the suspended floor insulation this is my preferred method. You can use cheaper mineral wool of course if woodfiber is out of your budget. 

 

https://www.ecologicalbuildingsystems.com/post/best-practice-approach-insulating-suspended-timber-floors

 

 

 

 

 

 

 

[Strangey71]

19 hours ago, Iceverge said:

 

You could easily get to 2-3 ACH50 with care. In any case airtighess makes no difference on a calm day. Without mechanical ventilation or a strong stack effect (heating on and windows open) your house will be stuffy.

 

My advice is to stay away from ASHPs in your case. A gas boiler will fit your expectations much closer. 

 

Regarding the suspended floor insulation this is my preferred method. You can use cheaper mineral wool of course if woodfiber is out of your budget. 

 

https://www.ecologicalbuildingsystems.com/post/best-practice-approach-insulating-suspended-timber-floors

 

 

 

 

 

 

 

Hiya, that looks like the most likely path forward. Thank you for that link that is probably how i’lll end up insulating under the floor.