Jump to content


ebuild is sad to announce its closure - it has become too time and resource intensive to develop, manage and maintain.

However, ebuild will remain on-line in archive mode (ie no posting facilties) for several weeks so that users can use it as an information resource.

4 Kwh/m2A Short Of A Picnic: Should I Care?


  • Please log in to reply
35 replies to this topic

#1 recoveringacademic

recoveringacademic

    Advanced Member

  • Moderators
  • 1,343 posts
  • LocationLancaster, Lancashire

Posted 15 January 2016 - 04:24 PM

We've messed about with PHPP for a bit and found that we can achieve 19kWh/m by making the house a bit cheaper. That's shorthand for making the windows smaller. It also makes the incidence of likely overheating an acceptable 10%. Dropping the specific heat demand to 15 is possible. Just. But the character of the house changes. It's mean.

In the original design, the light and the way that will plays with the inside of the house is what lit us up (apologies) about the design.

Should I care if the 'feel' of the house is compromised by the drive for lower energy requirement? I think so. I want to be delighted by the light. I want to feel the outside is inside. I want to watch the riot of goldfinches in the strong summer cross-light. I want to see the nesting kestrel from inside our house (its noisy mate alerted us to the nest in the first place).

Sod it, lets make the south and west windows a bit bigger.

#2 declan52

declan52

    Advanced Member

  • Members
  • PipPipPipPip
  • 3,087 posts
  • LocationCo. armagh

Posted 15 January 2016 - 04:30 PM

Nobody wants to live in a cave or a greenhouse so if you have a view you want to be able to sit in front of and look out I would put whatever size window I wanted.

#3 joiner

joiner

    Advanced Member

  • Moderators
  • 10,718 posts
  • LocationWest Midlands

Posted 15 January 2016 - 04:33 PM

Ian, calm down or you'll be living in a single room with lovely soft walls, having been taken there by some lovely understanding people in white coats driving a large white van with tinted windows. :unsure:

#4 Alphonsox

Alphonsox

    Advanced Member

  • Members
  • PipPipPipPip
  • 1,495 posts
  • LocationCounty Down, NI and Forest of Dean, England

Posted 15 January 2016 - 04:53 PM

View Postrecoveringacademic, on 15 January 2016 - 04:24 PM, said:

Dropping the specific heat demand to 15 is possible. Just. But the character of the house changes. It's mean.

You've answered you own question. Why on earth would you compromise the build to the point you find it "mean" just to satisfy an arbitrary target on a spreadsheet. Build the house you want, You're the one who's paying for it and the one who's going too have to live with the results

#5 recoveringacademic

recoveringacademic

    Advanced Member

  • Moderators
  • 1,343 posts
  • LocationLancaster, Lancashire

Posted 15 January 2016 - 04:59 PM

View Postjoiner, on 15 January 2016 - 04:33 PM, said:

calm down [...dear...] or you'll be living in a single room with lovely soft walls, having been taken there by some lovely understanding people in white coats driving a large white van with tinted windows. :unsure:

Understanding people, that's what I need.

#6 joiner

joiner

    Advanced Member

  • Moderators
  • 10,718 posts
  • LocationWest Midlands

Posted 15 January 2016 - 05:11 PM

There, there. Won't be long now.

#7 jsharris

jsharris

    Please ignore all posts by me, some are erroneous

  • Member Blogger
  • PipPipPipPip
  • 11,461 posts
  • LocationWiltshire/Dorset border

Posted 15 January 2016 - 05:12 PM

Just go for it. You'll probably still end up with a negative, or close to negative, energy house if you have a bit of PV on the roof, so I wouldn't get hung up on meeting a 30 year old German standard that was created before we had affordable small scale renewable generation.

#8 recoveringacademic

recoveringacademic

    Advanced Member

  • Moderators
  • 1,343 posts
  • LocationLancaster, Lancashire

Posted 15 January 2016 - 05:43 PM

View Postjsharris, on 15 January 2016 - 05:12 PM, said:

Just go for it.

That'll do for us. I'll ring the architect now. (Very nice man that Joiner bloke, very nice)

Edited by recoveringacademic, 15 January 2016 - 05:44 PM.


#9 reddal

reddal

    Regular Member

  • Members
  • PipPipPip
  • 237 posts

Posted 15 January 2016 - 06:50 PM

View Postrecoveringacademic, on 15 January 2016 - 04:24 PM, said:

Sod it, lets make the south and west windows a bit bigger.
We faced the same dilema when designing our house - we wanted lots of glass but knew this would compromise the heat losses.

We also said 'sod it' and built huge great walls of glass regardless (2 stories high!).

The effect is that the heating is a bit more expensive than it would have been with small windows. However its still pretty cheap to run the heating - a fraction of any other house I ever lived in. It does mean we do need the heating - its not like the heating hardly ever comes on like some people report - it comes on every day its cold outside (unless its sunny).

The bigger effect is we have to worry about cooling on sunny days.

Overall I have no regrets about all the glass. It makes the house nicer to live in - and that more than compensates for any downsides.

Design a house that will be a pleasure to own, look at and live in - then work out how to use technology etc to make that work best.

- reddal

#10 1anR

1anR

    Regular Member

  • Members
  • PipPipPip
  • 271 posts

Posted 15 January 2016 - 07:29 PM

As others have said, you should absolutely not compromise what excites you about the house to achieve an arbitrary target. Unless of course what excites you is PH Certification, which it clearly is not.

The "compromise" looks like it is costing you an additional 27% space heating cost. I bet that's 27% of quite a small figure, and a much smaller percentage of your overall energy requirement.

However, I think you should mitigate the 10% overheating risk. I'm surprised PHPP has this as "acceptable" (but I know it does). I believe that 10% overheating is classed as 10% of the total hours in a year when the property is over 25 degrees, day or night. But unfortunately it doesn't quantify maximum temperatures. 25 degree night time temperatures would upset my sleep pattern, but 27 or 30 I'd find really uncomfortable.

The PHPP classification for over heating is: 0-2 Excellent, 2-5 Good, 5-10 acceptable.

While the calculation is based on a very conservative ventilation scenario, ie closed windows, I think you are best to try and get into at least in the "Good" range. Unless you know you have strategies for performing much better than calculated by perhaps having good positioning of windows across the house in line with the prevailing wind that can securely be left open.

#11 Markblox

Markblox

    Regular Member

  • Members
  • PipPipPip
  • 136 posts

Posted 15 January 2016 - 08:28 PM

View Post1anR, on 15 January 2016 - 07:29 PM, said:

As others have said, you should absolutely not compromise what excites you about the house to achieve an arbitrary target. Unless of course what excites you is PH Certification, which it clearly is not.

The "compromise" looks like it is costing you an additional 27% space heating cost. I bet that's 27% of quite a small figure, and a much smaller percentage of your overall energy requirement.

However, I think you should mitigate the 10% overheating risk. I'm surprised PHPP has this as "acceptable" (but I know it does). I believe that 10% overheating is classed as 10% of the total hours in a year when the property is over 25 degrees, day or night. But unfortunately it doesn't quantify maximum temperatures. 25 degree night time temperatures would upset my sleep pattern, but 27 or 30 I'd find really uncomfortable.

The PHPP classification for over heating is: 0-2 Excellent, 2-5 Good, 5-10 acceptable.

While the calculation is based on a very conservative ventilation scenario, ie closed windows, I think you are best to try and get into at least in the "Good" range. Unless you know you have strategies for performing much better than calculated by perhaps having good positioning of windows across the house in line with the prevailing wind that can securely be left open.
How about plenty of glass with some external blinds linked to temperature stats? Best of both worlds.

#12 1anR

1anR

    Regular Member

  • Members
  • PipPipPip
  • 271 posts

Posted 15 January 2016 - 08:33 PM

View PostMarkblox, on 15 January 2016 - 08:28 PM, said:


How about plenty of glass with some external blinds linked to temperature stats? Best of both worlds.
That's just what I'm doing. Plus some stack ventilation and hopefully some passive cooling of the slab.

#13 NSS

NSS

    Regular Member

  • Member Blogger
  • PipPipPip
  • 183 posts

Posted 15 January 2016 - 08:39 PM

My SageGlass panels arrived from the US earlier this week. Internorm are coming back to install early Feb, though it will be a while before they're commissioned and I can report on how effective they are. Still, you never know but we may actually get some decent sunshine by then!

#14 Triassic

Triassic

    Advanced Member

  • Members
  • PipPipPipPip
  • 1,239 posts
  • LocationCumbria

Posted 15 January 2016 - 08:54 PM

I've got to an age where I'm going to build something I want to live in, that will be warm in winter and cool in summer and not something that will meet targets or win awards. I might just blow the contingency on something whimsical, there again, maybe not!

#15 VIPMan

VIPMan

    Member

  • Members
  • PipPip
  • 59 posts
  • LocationLancaster

Posted 15 January 2016 - 09:12 PM

On a 150 sq metre TFA this only amounts to 600 kWh a year. Not something that strikes me as an issue unless it causes other design changes which drive costs or create complications elsewhere. I assume this is the result with an assumed default 0.6 air changes per hour in your PHPP spreadsheet - good builders should be able to do much better than this on a new build and this would get you much nearer 15 kWh Picnic limit by itself.

I would be much more concerned with the overheating result and believe steps should be taken to mitigate this if the house is to be comfortable in summer (even Bay Horse sees some sunshine!) A few deciduous trees in the correct location may be all that is needed.

#16 recoveringacademic

recoveringacademic

    Advanced Member

  • Moderators
  • 1,343 posts
  • LocationLancaster, Lancashire

Posted 15 January 2016 - 09:18 PM

View PostVIPMan, on 15 January 2016 - 09:12 PM, said:

I would be much more concerned with the overheating result and believe steps should be taken to mitigate this if the house is to be comfortable in summer (even Bay Horse sees some sunshine!) A few deciduous trees in the correct location may be all that is needed.

Shutters in design even as you speak.... out of self made (not grown) oak and larch slats.... and we thought we'd mess about with a thick, toughened glass brise soleil. Maybe 10 inches or so on the south facing windows. Should be fun!

#17 TerryE

TerryE

    Regular Member

  • Member Blogger
  • PipPipPip
  • 709 posts
  • LocationSouth Northants

Posted 16 January 2016 - 12:21 AM

There is absolutely nothing wrong with more window space -- except that you need check both your heating and cooling design. IMO for a passivHaus class build, the latter is more of an issue than the former. Why not go for it, so long a you ensure that your design can dump the excess kW?

BTW what kind of oak isn't grown -- other than the plastic oak-effect kind? :wacko:

#18 ConstructionChannel

ConstructionChannel

    Local Youtuber

  • Members
  • PipPipPipPip
  • 1,723 posts
  • LocationNW Essex

Posted 16 January 2016 - 12:39 AM

FWIW do you want a bigger window?...........then put a bigger window in!

Edited by ConstructionChannel, 16 January 2016 - 12:45 AM.


#19 joiner

joiner

    Advanced Member

  • Moderators
  • 10,718 posts
  • LocationWest Midlands

Posted 16 January 2016 - 07:48 AM

Just don't tell anyone. :rolleyes:

#20 PeterStarck

PeterStarck

    Regular Member

  • Member Blogger
  • PipPipPip
  • 144 posts
  • LocationEast Kent

Posted 16 January 2016 - 08:37 AM

View Postrecoveringacademic, on 15 January 2016 - 04:24 PM, said:

I want to watch the riot of goldfinches in the strong summer cross-light. I want to see the nesting kestrel from inside our house (its noisy mate alerted us to the nest in the first place).

Sounds a fantastic place, make the most of it, and like you say 'Sod It'.