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4 minutes ago, joe90 said:

Actually I am not bothered about it, but it’s a bit of a competition on here to do well, is it not ? 🤔

What really matters is actual annual energy bill, and I suspect Jeremy would get the prize for that one.

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5 minutes ago, joe90 said:

Actually I am not bothered about it, but it’s a bit of a competition on here to do well, is it not ? 🤔

 

Not sure it is, really.  There's a farm building conversion a few miles from here that has an EPC of A138.  The house is pretty poor thermally, not a lot better than building regs.  It gets the very high EPC because two of the attached barns have roofs that are covered in PV panels.  IIRC it has something like 30 kWp or so, and somehow that lot got included in the EPC for the converted house.

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Posted (edited)
2 hours ago, joe90 said:

Actually I am not bothered about it, but it’s a bit of a competition on here to do well, is it not ? 🤔

 

Have to get mine done again, so I can boast that it beats a Passivehaus. Currently 74 at 2000 sqft, but has had a 10kWp solar array added since 🤠.

 

It currently says that 2.5kWp will put me up to 83 Hope it is linear, then I get 110. 

 

Bet it isn’t though.

 

F

Edited by Ferdinand
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I went from 84, pre PV (FiT requirement) to 103 with 9.7kW of PV.

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Does show that designing in PV from the very beginning is worthwhile.

 

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On 21/06/2019 at 19:27, ProDave said:

What really matters is actual annual energy bill, and I suspect Jeremy would get the prize for that one.

 

Agree, plus general comfort level (especially in summer). For a close on 400m2 house, we're averaging about £1/day gas and 83p/day electricity once the FIT is taken into account.

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1 minute ago, Bitpipe said:

For a close on 400m2 house, we're averaging about £1/day gas and 83p/day electricity once the FIT is taken into account.

Or about a quarter of what I pay on a m2 basis.

Small houses look terrible on paper and are even worse to live in.

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Just now, SteamyTea said:

Or about a quarter of what I pay on a m2 basis.

Small houses look terrible on paper and are even worse to live in.

 

To be fair, we're not using the rooms in roof regularly (extra guest bedrooms) and the basement is about half occupied (still full of post moving in junk) so the per m2 is probably not as low as it looks.

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39 minutes ago, Bitpipe said:

 

To be fair, we're not using the rooms in roof regularly

I tend to live in my kitchen, not sat on my sofa for years now.

Last year I did heat the house during the winter because I am getting weedy.  Though the heating is only two storage heater with a combined maximum capacity of 22.5 kWh/day.

My biggest usage is DHW, but that is because I like a bath, a deep one, every day, sometimes twice a day.

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wouldn't worry about it @joe90 you've built a nice comfortable house now to enjoy (/garden!). What air tight detail did you do in your loft? Membrane or smart ply?

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10 minutes ago, Oz07 said:

wouldn't worry about it @joe90 you've built a nice comfortable house now to enjoy (/garden!). What air tight detail did you do in your loft? Membrane or smart ply?

 

After reading lengthy posts about it I used OSB (smart ply) bubble glued on all joins. The join to the wall/rafters was the most difficult but I just foamed it to death. When we did the airtest we first kept the loft hatch closed (rubber seal) then opened it to see the difference, after an initial surge (to pressurise/de-pressurise the loft space) the figures didn’t change much at all so I am pleased with it.

 

note, rather than try to land all joins on rafters (not possible with horizontal joins) I installed whole sheets so the joins were between rafters and glues osb strips to overlap all joins. It was less tricky this way and I had less waste. As it was a hip roof I also glued a strip down the hip inside to make sure.

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13 minutes ago, joe90 said:

After reading lengthy posts about it I used OSB (smart ply) bubble glued on all joins.

While I think of it, do you know the U-Value of your roof, is there insulation between the upstairs ceiling the the loft floor?

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19 minutes ago, SteamyTea said:

While I think of it, do you know the U-Value of your roof, is there insulation between the upstairs ceiling the the loft floor?

 

No insulation installed as the loft is a warm loft, so house should all be the same temp. U value given as 0.14.

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@joe90 is the airtight osb a specific product? What's the cost? Cheaper than membranes?

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2 minutes ago, Oz07 said:

@joe90 is the airtight osb a specific product? What's the cost? Cheaper than membranes?

 

I have read that OSB generally is “vapour open” I.e. it breaths (which I think is a good thing) but is airtight. My air test supports this. I ordered I think it was 12mm smartly, it had no tongue and groove but my overlap strips made it airtight with glue. I am not a fan of membranes and sticky tape.

6 minutes ago, SteamyTea said:

May use that as an example of 'thermal mass'

 

Wash your mouth out with soap and water before @JSHarris reads that 🤣🤣🤣🤣🤣

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5 hours ago, joe90 said:

I have read that OSB generally is “vapour open” I.e. it breaths (which I think is a good thing) but is airtight. My air test supports this. I ordered I think it was 12mm smartly, it had no tongue and groove but my overlap strips made it airtight with glue. I am not a fan of membranes and sticky tape.

 

I was asking about this over here too... Smartply Pro-passive OSB3 is tested / certified for airtightness, and also its tech data states it is a vapour barrier / vapour control layer. 

 

So it seems either use a cheaper/non-certified OSB if you want vapour open, and risk it not being airtight, or use the Pro-passive and deal with it being VCL. I think in practice it doesn't matter too much as even an "vapour open" wall construction generally calls for the inner layer to be the least vapour permeable (e.g. by factor 3:1 called for the Cotterell Passive house handbook)

 

 

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we are using the propassive as the VPL / racking layer (on warm side of wall), with woodfibre insulation between and solid wood fibre external wrap

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