Notes from an eco house. (2025 Update)

It's worth it - if you're OK with spreadsheets. I see you've had a go at calculating heat loss further down this thread - I'd guess you're underestimating heat loss by a factor of about 3 using whatever method you've used.

It takes a while to set up, and took me an hour or so to do my home. The good thing is you can tweak the variables to suit your circumstances. For example, I very rarely heat a room to 21C - it's simply too warm for me. But putting in standard variables helps with design, estimating improvements, and highlighting problems.

I don't think so - 2"?! But if your rooms are quite small, yes, it can be a problem. If you put the PIR in alcoves you'd barely notice. Also, if you go back to brick, you'd likely find the space loss barely noticeable.

Yes. Over WP plasterboard.

Yes, plasterboard layer. And with it some pain if needing to wall mount anything heavy. But there are loads of workarounds.

With reveals I've had to cut down the insulation to 25mm. And again plenty of workarounds for wiring and plumbing. The biggest issue I have had is with elaborate skirting boards that need to be retained. That can be a pain.

Well, live and learn.

I'd be interested, if you have the time/inclination, to see any examples on Rightmove, street view etc.

Yes - outbuilding maybe. But not part of the main house IME.

They'd be available if you know what it's made of. This is the most comprehensive database I've found:

One additional problem I have is working out the temperatures within these sandwiched materials - where the brick ends and the insulation starts, say. So I just guess.

https://www.google.co.uk/maps/@52.2827805,0.2140835,3a,75y,96.25h,75.13t/data=!3m7!1e1!3m5!1sZwNKBCPMKHPhM0fa_BcF2w!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D14.865931915613402%26panoid%3DZwNKBCPMKHPhM0fa_BcF2w%26yaw%3D96.25213706096844!7i13312!8i6656?entry=ttu&g_ep=EgoyMDI0MTIxMS4wIKXMDSoASAFQAw%3D%3D At least the porch and rear extension are single 4.5" brick and I am fairly sure that the main house was too.

https://www.google.co.uk/maps/@52.1986602,0.1458007,3a,75y,79.98h,87.28t/data=!3m7!1e1!3m5!1sC6vN2Kdli_JQDpjcemGaxA!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D2.7213018781475853%26panoid%3DC6vN2Kdli_JQDpjcemGaxA%26yaw%3D79.97823316732611!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI0MTIxMS4wIKXMDSoASAFQAw%3D%3D Catharine Street Cambridge. Outside walls 4.5" brick as discovered when drilling into one and the brick fell out. It wasn't even a whole prick.

https://www.google.co.uk/maps/@51.5467208,-0.1646949,3a,75y,119.66h,105.83t/data=!3m7!1e1!3m5!1sMXxpTEzxinYJVUyvRbz_tQ!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D-15.826122642135488%26panoid%3DMXxpTEzxinYJVUyvRbz_tQ%26yaw%3D119.66173668119905!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI0MTIxMS4wIKXMDSoASAFQAw%3D%3D

Where it says Art College was Andy Dawson's Rally Garage. I lived in the top flat. we know it was single brick because it had an open fireplace and not only did we get the whole wall glowing red hot, as seen from *outside* we poked a poker through the mortar!

Thanks!

What I don't understand on that street is why there's so many half bricks. I always thought regularly spaced headers were a sure indication of a 9" solid brick wall. The bond can be seen clearly at ground level - looks like a classic 9" solid type to me?!

An occasional half brick on a 4.5" wall certainly, for spacing around openings. But why so many, between the openings?

Looks very ropey. Bit like my old east London terrace, very soft bricks. But again whole rows of headers - a classic 9" solid wall bond, I thought. I don't doubt your expereince. I just don't understand why they built them that way, instead of using a stretcher bond (almost) throughout.

I never did work on the street facing walls. Perhaps they are faked to look thick, Perhaps they wer thick. Bu the sidewall into the passage and the rear extension were all 4.5"

You cant see any bricks., It is all rendered, It was originally a stables, then a set of mews garages with accomodation above.

Thats what they do or did in France most all i know over there use electric heating, all that Nuclear capacity they have eh;?...

In message <vl8or3$3tkg1$ snipped-for-privacy@dont-email.me, at 13:31:15 on Fri, 3 Jan

I do "get it", because this debate is simple about the [allegedly catastrophic] loss through that one wall. The other losses will be the same whatever the construction of that wall.

But with a big hole for a window.

So the window is more lossy than my solid brick wall?

Hence saving a couple of hundred watts by going from a solid brick wall to a cavity insulated one, isn't significant. That's what I said from the start.

Modern houses reduce all the losses. All we should be interested in here is the difference between a hundred year old house with a solid brick wall, and a hypothetical hundred year old house with a cavity wall.

Then its around a 40% difference between a ~200mm solid wall compared to a ~250mm double brick with 50mm cavity wall. If the solid wall loses 500 watts, the cavity wall loses ~330. Yes, your windows, unless quite modern, will be less insulating than a cavity brick wall. Typical U values of modern windows can be as low as

Last time I did the calcs the walls with greater area represented more loss than a single glazed window in most cases.

In fact installing DG is probably the least effective way to reduce heatlosss except that it usually is draught proof.

In message <vl8ths$3uotg$ snipped-for-privacy@dont-email.me, at 14:51:40 on Fri, 3 Jan

The method I used was to extrapolate from someone else's numbers. If those were wrong, go yell at them not me.

In message <vl9249$3vl03$ snipped-for-privacy@dont-email.me, at 16:09:45 on Fri, 3 Jan

Integral garages too.

It depends on the size of the windows vs surface area of the walls . My

Just an observation with respect to my 1908 property.

Solid 9 inch brick with approx 1 inch of old type plaster. Before I renovated the old skirting boards were approx 18 inches high but with no plaster behind them, just a 1 inch void to the wall, and hiding a gap between the edge of the floor boards on a suspended floor and the wall. The effective U value for that 18 inches was that of a 1/2 inch of wood.

My "ornate" skirting board were replaced with something a lot smaller and of a square profile. Really too much hassle to retain the old skirting boards. The wood was dry and brittle and instantly split when trying to remove them. Attached to wooden wedges in the brick work with large cut nails. They were also heavily "painted" with a brown varnish that turned to an industrial strength tar like like substance when trying to strip them with chemicals or with a heat gun.

Splendid isolation especially if your a hi-fi nut or a rock muso:)..

Yep back in 78 was looking to buy a house there but patriarchal building society manager said No!, its got a 4.5 inch single end wall you can do better and we did.

Those streets are going be a real PITA for EV charging mind you in Cambridge the local council would prefer you to walk or use your push bike and abandon the car!..

Grew up in one like that, remember my old dad using a rawlplug tool to put some brackets on the end wall for the TV aerial, took him a whole bloody day to make the holes.

In more recent years the first SDS drill i had when through it as if the wall wasn't there!...

Indeed

Frankly they need tearing down.

But you don't want to own a car if you live inside Cambridge. Not even an EV.