'Deep' eco retrofit in Glocestershire

[ig218]

Hi Build Hub,

 

I'm just about to dive into a big retrofit of a detached house (with the help of a general builder). Kicking off with a self-build garage/workshop. Over the past 6 months I've been furiously reading the internet and these forums and watching too much youtube from near and far on how to build timber frame, how to retrofit, and where the latest thinking is on high-tech/high-efficiency building methods and technologies - though I'm much more inclined towards low-tech/high-efficiency everything.

Self build garage-workshop: We have an insulated foundation going down in June (subcontracted) with a self build stick frame going up thereafter. We're within permitted development and under 30 sqm, but still sticking close to building regs as we want it to be comfortable for overnight guests and ourselves.

 

Main house: planning granted and structural engineer just finished calcs so building regs should be finished shortly. The house has been completely stripped back to the original fabric in prep for kickoff as soon as all the paperwork is signed and stamped. It's a 1900s or so, solid brick construction detached house. We're planning tons of EWI and a warm roof along with an insulated concrete base and trying to achieve very high levels of airtightness. Basic PHPP calcs predict the house performing at about 32 kW/m2.a, so at 145 sqm thats just under £700/yr at current electricity prices. Not as low as I'd like it to be - but I'm a cheapo... Solar PV and renewable heat kicked to future once the bank account has recovered... MVHR is lined up, the primary heating strategy will be a gas boiler (as there was a brand new one in when we bought the place).

 

Oh - and the only reason we're doing this is because the house was practically unliveable when it found us. From all the chat with building industry people it seems an extensive whole-house retrofit is not that common (is this true? I find that hard to believe, but then again I don't see so many examples) - so if there's healthy interest in any of the above I'd be happy to share as it goes along.

 

There were bat surveys, but no bats in the end. There WAS a large amount of asbestos... (that word 'was' cost a pretty penny). There is still a healthy amount of woodworm and damp - though taking decades of non-breathable material off the inside might have helped that. The concrete render externally definitely didn't!

 

Me: I'm a mechanical engineer turned industrial desiger and I cut my teeth in aerospace manufacturing. I've been told I'm about to 'graduate' from aerospace tolerances to building industry tolerances - I obsess over details - too much my SO would say, and I'm afraid of getting things wrong... that might have to change!

 

Here's a selection of photos. If anyone's interested please do comment why and it'll influence what I share. And a big thank you to the forum as it's all been invaluable already!

[Mr Punter]

Someone called shevek at Green Building Forum did an eco retrofit (Enerphit?) and posted much about it.  May be a good contact.

[SteamyTea]

8 hours ago, ig218 said:

Basic PHPP calcs predict the house performing at about 32 kW/m2.a, so at 145 sqm thats just under £700/yr at current electricity prices.

Do you mean 32 kWh/m².a ?

  

8 hours ago, ig218 said:

Solar PV and renewable heat kicked to future once the bank account has recovered... MVHR is lined up

If you have to re-roof, then consider roof integrated PV, about the same price as slates.

You have to design in for an ASHP at this stage.

MVHR relies on very good airtightness results >2.5 ACH is often quoted.

Edited June 4, 2021 by SteamyTea

[ig218]

Thanks @Mr Punter, shevek is prolific on Green Building Forum but I can't seem to find his own thread - if it exists. Do you remember the name of it by chance?

 

@SteamyTea, yes thanks, typo dropped the h. 32 kWh/m2a. Not mind blowing, but a neighbour only heats their living room in a ginormous house, and we'd like to avoid that. Our family has the tropics in our blood so warmth is really important... Stories of passive house heating systems that run for hours an entire winter make me drool.

 

Thanks for the tips. Reroofing is happening, so will look into integrated PV. New-to-me technology - I had always envisaged an array of PV panels. Are integrated PV panels well proven today? No one else has suggested it so far though I've seen it at NHBRC (tucked away on a corner...) and paid it as much attention.

Designing in ASHP - what does that entail? I've umm-ed and aah-ed about getting professionals engaged to really figure out the future heating strategy. e.g. answering questions like - do we need radiators upstairs at all (I bet yes). If so what size rads, and therefore what size ASHP will be needed in future if it's even feasible. We're putting UFH into the ground floor slab so the downstairs is taken care of in the short and long term AFAIA. As for upstairs, the current idea is having electrics installed for future electric rads if/when required for top up heat. (SO wants an electric radiant heat panel in the bathroom, she's not from around here...)

 

I can see now if we're going to bother with ASHP in future may as well use the warm water to heat rads upstairs rather than electric... haven't mentioned domestic hot water yet!

 

Would love to hear your thoughts on heating strategy.

[SteamyTea]

Do a lot of searching and reading, on here and your problems will be solved.

You can use Google's site: prefix as I don't find the built in search that good. You will even find a topic on searching.

 

The main thing to keep in mind is that prices vary a lot. So you can save lots of cash by buying sensibly.

 

A decent HP heating system will be on a lot, but not always heating.

A gas or oil system does not work in the same fashion, it over heats, then over cools, to a greater degree than a HP based system.

The actual energy losses from the building will be the same over a period of time, just that every time it fires up, and shut down, the efficiency takes a big hit.

It is like my driving, usually get low 50 MPG from my car, but this week, with all the holiday traffic about I get mid 40s, because I have to keep stopping and starting as Emmets find Cornish roundabouts and left hand turns different than the rest of the country for some reason. They are the place to suddenly stop and point at St. Michael's Mount, or a seagull, and argue with the kids. 

Edited June 5, 2021 by SteamyTea

[Ferdinand]

How did the asbestos get into a 1900 house?

 

This is integrated solar on the right:

 

 

There is a membrane like the 25 year pond-liner stuff (HDPE ? EDPM ?) under the panels, and no tiles. And some sort of mounting system.

 

F

[SteamyTea]

1 hour ago, Ferdinand said:

This is integrated solar on the right:

It uses the https://www.segen.co.uk/gse/ system.

Shop about and the panels (not the modules)  are about 30 quid each.

 

(it is a shame that Jeremy built in some shading)

Edited June 5, 2021 by SteamyTea

[ig218]

I see, integrated solar not solar tiles. Thanks.

 

@Ferdinand I presume the asbestos all arrived sometime after 1970? There was a lot of it. Ceiling boards in bathroom, wall boards in the kitchen, there were a bunch of old asbestos roof tile fragments in piles in the garden and an eyebrow-raising amount *underneath* the prefab-concrete garage's concrete slab! The original clay sewage pipes were broken up in the earth and in it's place the fibrous stuff which I think had trace amounts? (Something contaminated a pile of excavated earth...) Also lots of styrofoam adhered to the walls internally - with toxic smoke locked inside it... anyway, all gone now. Back to brick and timber... and woodworm.The previous owner was clearly 'handy' but the house when it came it us fell to the deep end of the 'in need of modernisation' category.

 

@SteamyTea is this *the* famous JHarris' build?

[Ferdinand]

5 minutes ago, ig218 said:

I see, integrated solar not solar tiles. Thanks.

 

@Ferdinand I presume the asbestos all arrived sometime after 1970? There was a lot of it. Ceiling boards in bathroom, wall boards in the kitchen, there were a bunch of old asbestos roof tile fragments in piles in the garden and an eyebrow-raising amount *underneath* the prefab-concrete garage's concrete slab! The original clay sewage pipes were broken up in the earth and in it's place the fibrous stuff which I think had trace amounts? (Something contaminated a pile of excavated earth...) Also lots of styrofoam adhered to the walls internally - with toxic smoke locked inside it... anyway, all gone now. Back to brick and timber... and woodworm.The previous owner was clearly 'handy' but the house when it came it us fell to the deep end of the 'in need of modernisation' category.

 

@SteamyTea is this *the* famous JHarris' build?

 

Yes.

 

It's the blog header.

 

If you want to read it put the links form here into archive.org.

 

 

[SteamyTea]

1 minute ago, ig218 said:

@SteamyTea is this *the* famous JHarris' build

Yes.

When I went there, I did not notice the modules on his roof, which was strange as I knew they were there, and I was involved in the business at the time.