House Design, thoughts appreciated

[charlieb]

Hi folks,

I'm in the process of designing (pre-architect) a farm house for a site in SE Scotland. Chances are I'll never get planning permission, but I'm thoroughly enjoying playing around with design ideas in my head, and getting inspiration from any and all (eco) new houses I see in the countryside.  I've done some drawings, so I'd be interested in people's thoughts (assuming I manage to upload..).

The site is a North Facing quarry (really just a hole in the ground, perhaps 70m across).  Hopefully you'll see from the pics that the house would be two storeys, with the upper (living) story facing North and South, while the lower (sleeping) storey would  just face North.  Yes, I know the siting doesn't optimise solar gain, but I think the design does pretty well, and this is the best location for a number of reasons (not least S facing garden).    As you can see, most of the S facing wall is glass, including conservatory on the kitchen, and a veranda type thing off the living room.  Heating is by big woodstove in the hall, with backboiler doing DHW and minimal downstairs radiators from a huge thermal store in the loft, and a smaller stove in the living room/study. Wood store is under the East-wall balcony, with a window for throwing logs through into the hall.   Also solar thermal on the South facing roof.   Leccy almost certainly mains connected, but PV on the rest of the S facing roof, and it's a good site for small wind so could easily be carbon negative.   Water would be connected directly into a private water supply that runs right past.     Structure remains to be seen, but probably timber frame straw bale on the W/N/E walls, timber frame and some other insulation on the South Face.  Roof may be just corrugated iron if I can get away with it.  I have access to standing wood of most sorts, so would buy a woodmizer and cut all the wood myself.

I'd be interested in thoughts on the likes of:

• Is it worth building internal walls/floors  with stone to increase thermal mass?
• How big (volume) would the thermal store need to be to provide central heating for say 4 hours?

Yay.  I managed to insert the images (thanks Martin for clear instructions). If you're wondering why the random 1st floor door onto nothin on the W wall, it's because I'd like to have the option of adding a (probably turf roofed) annex with one or two extra bedrooms. -  A WWOOFER's hobbit hole.   Door would then give out straight onto the turf roof which would lead straight onto the top of the quarry.

[brackwell]

In answer to thermal storage capacity etc.

I recommend you read "designing comfortable homes" from www.cca.org.nz

Ken

[biff]

it looks like a very intresting plan and i wish you luck in your project. the only thing i would try and change is the stairs. after all my life in the building its straights flights for me.spiral never lives up to its expectations and they are accident prone no matter how well they are done.
                                                                                                                biff

[A.L.]

hello,

I am going to assume a  120m² house with the bedrooms on the lower floor.

If walls, floor and loft are insulated to 0.12-0.15w/m²°C and infiltration is limited to 1-2m³/m².hr and a mechanical heat recovery ventilation system fitted, daily heat requirement of an normally occupied house would be no more than 20kWh/day at an external temp of 0°C.

30m³ of stone/concrete or equivalent thermal mass would liberate 20kWh with a 1-1.5°C fall in temperature and a continuous 2-2.5kW input would be more than sufficient to meet all likely heating + DHW demand. Thus with good controls a thermal store for space heating could be largely avoided, the bottom of say a 300l DHW thermal should be sufficient. My preference would be for a concrete floor slab ufh downstairs with ufh on a timber floor upstairs. Note I believe in continuous heating to keep peak loads minimised.

With a house insulated to this level prevention of summer overheating by shading the south facing windows would be a prerequisite.

Oh! - and get that flue off the south roof! do not want shadows on your future P.V. ! 

[dhaslam]

It would be better to dig  out the area behind the house to allow sunlight into the  south facing  ground floor rooms.  Apart from  heat gain it would make a big difference to the light inside the house.  Having to have lights on all day  isn't  good.

[charlieb]

Many thanks guys.  Biff, I take your point.  Will have a think about options (although there is some future-proofing in the design in that there's a ground level door on both floors - I should never need a chair lift in this house).

Brckwell. I've downloaded that doc ready to read on a train some time. Looks interesting.   And A.L that sounds like good news  - a 300l hot water tank seems perfectly feasible.  I certainly do plan to insulate to the max (deciduous plants on the South Face is the main plan for shading, but also the veranda and conservatory will probably have opaque rooves) but it's a farmhouse, so people will be in and out all the time and I reckon infiltration would be a bit higher.  Hence the two stoves that could give me a lot of output between them.  I'm not so keen on underfloor - mostly because I want everything in this house to be easily DIYable, but also because the downstairs rooms will be completely unoccupied during the day so continuous seems a waste of energy. I'm thinking skirting hot pipes or something, with most of the heat coming directly from the stoves as and when it's needed (I'm not a fan of constant-temperature warm houses. I don't mind one bit wearing a woolly jumper untill the living room's warmed up a bit).

DHaslam, digging out the back isn't an option at all.  But the north facing lower rooms will only be occupied at night and early morning/late evening when there'll actually be quite a lot of light (I've thought hard about where I want to get morning and evening light - getting evening light to the kitchen is as much of an issue for me).  I'll certainly look at light-tube options for the corridor/shower room at the back though.

   

[DominicJ]

I have almost no knowledge of construction or building, but here goes.

You dont want your main entrance to be downstairs, and your kitchen upstairs.  Lugging your shopping up the stairs isnt fun.
You REALLY dont want external stairs up to your front door as your only way in.  There are loads of houses like that near me, an I dont know anyone of the residents who like them, quite a few have added doors, or use the garage door as the main entrance.  If your main entrance is on the hill side, thats different and the lay out makes sense.
If you disagree, spend the next few weeks taking your shopping upstairs before you put it in the fridge, then imagine dragging it up a rickety external stair case in the rain/snow/hail.

Add a porch to your entrances, and you deal with a lot of the in/out heat loss.

"Underfloor" is frequently taken to be something that really it isnt.
Yes you can add several hundred tons of concrete and run pipes through them, but I dont believe thats the only "under floor" option.  Assuming you have suspended wooden floors, and its legal to do so, simply clip a length of suitable piping to the undersides of the flooring joists.  Straight away, you have heat, under the floor.  You reclaim the space from the radiators, but you dont gain any thermal mass either.

Worrying about heating empty rooms is a bit of a red herring I think (again, no great knowledge) the vast majority of the heat "lost" from the downstairs bedrooms will simply migrate to the upstairs living area, and then up to the roof and out.
Very little will be out through the walls.

Just wait till you start trying to put room dimensions together and justifying 3ft thick internal walls

[dhaslam]

The  Grand Designs house  in Cumbria is a good example of how not to build a house.  It is pretty miserable with rooms without windows and despite the conservatory that gets very hot during the day the rest of the house stays quite cold and damp, needing a de-humidifier according to the linked RAE report.   Also the access to the house is down a long flight of steps and then up a stairs inside the house.     Probably the worst house of all the Grand Designs.     

http://www.visitcumbria.com/pen/underground-house.htm

[JohnS]

You are being a bit hard on the house.  Whilst I agree with the darkness in the back rooms, it is difficult to tell if the damp and dehumidifiers were because of the building drying out and the waterproofing problem.

It would be nice to have an update on how it has worked in practice.

Mind you 500w of PV is a bit of a joke but it was 2002.

[charlieb]

Thanks DomJ.  That's exactly the sort of comment I'm after. Remains to be seen where the car would be parked (probably below, but could equally be above), but one option could be to include a pulley lift in the two-level bit - I'd kind of been thinking about doing that anyway so someone in a wheelchair could pulley themselves up and down from downstairs hall to upstairs kitchen.  Logs for the upstairs stove would go up that way too from the downstairs stove...

The site is actually quite like the underground house site, but I am definitely NOT planning to build anything underground. The quarry is North facing - so my design has the upper stories well a bove the quarryside. Both North facing stories have small windows in all rooms, except upstairs where the views are amazing.    That said, the back of the ground floor will be up against the quarryside, so I'll have to think hard about damp-proofing that (I have a '500 dollars and under' (or somesuch) book about building underground houses - has a lot of good stuff, but just a bit too hippy for me to take seriously).

[clockmanFR]

charlieb,

You have a golden opportunity to build in to the ground and use the ground as your stable heat source is the way to go.

However, finding a good Engineer to assess the quarry stone and its stability is another matter as in this day and age most would not even try to evaluate.

Looking at your drawings it could be possible to build a serious damproof wall with internal drainage within the quarry that would funnel any water around your house, and then balance the house structure against your new waterproof quarry wall. But getting a builder to do this will be a no no as its not in the normal "box" and unlikely that they want to get involved, especially in the UK.

It can be done, and i have seen it done, but find a friendly engineer that can just do a preliminary examination before doing a full report. I think Building regs will want to see a report.

[charlieb]

Yep, I forgot to finish my post last night.  It should have finished with 'so I'll have to think hard about damp-proofing..... and whether I can take advantage of the thermal mass in the bedrock/soil'.   

'Quarry' is perhaps too grand a word for the site.  More of a hole in the edge of a bank where soil and hard toppings have been dug out with tractors over the years.  The bedrock's lowland glacial deposits (a flakey, shaley mess. Good for filling in pot holes but not much else), under a heavy clay soil. Where there's actual stone it'll be sandstone. 

Next step is to get the site properly surveyed - at the moment I'm guessing on height of the quarryside at various points.

[charlieb]

I had a read of that thermal mass/insulation booklet from NZ on the train south last weekend and would thoroughly recomend it.  Read it pretty much cover to cover on a computer, which is unheard of.   Has simple rules of thumb for many scenarios, and is relevant for exactly the stage in planning/design that I've got to. Seriously useful (assuming you're clued up enough to switch N and S but not E and W).

[rt29781]

Has anyone actually tried ufh by clipping the pipes to the underside of a wooden floor and then insulating beneath the pipes.  I have previously embedded the pipes into concrete and that worked well.  However for our new house in Aberdeen clipping the pipes to the ground floor beams would be so simple and allow me to get rid of the radiators........

[brackwell]

rt,

sounds a good idea. I have done CH pipes and HW pipes so why not expand the idea further!   Mind you the heat transfer will be by conduction so maybe one needs to fasten it to the underside of the floor boards, but maybe conduction rates are not fast enough to allow this to work but then as you say it does work for concrete.

Ken