Optimum size for new home

Post by **adam2** » 08 Jun 2013, 12:54

Friends are soon moving to North Somerset with the aim of living a low impact lifestyle and producing a fair bit of their own food.

The property in question is a bank forclosure and consists of a pair of modern semidetached houses, in a very poor state.
Both are heavily vandalised and weather damaged.

Demolition and building new seems the best option, recycling and reusing bricks and roof tiles if possible.
Planning should not be a problem provided that the new structure is no larger than that to be demolished.

Mains water is available, electricity MIGHT be available, mains gas no way.

Two adults and 2 kids, no more expected.

Many respected members of these forums speak of the merits of small or compact dwellings, pointing out the reduced capital costs and heating requirement.
I would favour something more spacious but designed with minimal energy use in mind.

Loft space, light storage, water tank, F+E tank

Upstairs
4 bedrooms, one being a spare room
Shower room with WC
Bathroom with WC
Large store, slightly warmed by hot water tank, for linen, blankets, out of season clothing etc.

Ground floor
Large open plan living room/cooking area/dining area. Equiped with solid fuel cooker.
Access from the outside into this area being via an insulated porch or lobby in which outdoor boots or clothing and cycles may be left.
Dry goods store, vermin proof for dried foods
Larder, on north side and designed to be as cool as possible.
Workshop and related storage, equiped with workbenches and shelves/racking.
Utility room for freezers, washing machine, and possibly brewing/wine making equipment.
The workshop would have an internal door from the open plan cooking/dining/living area, and also it own door out to the garden, thereby avoiding taking dirty or awkward articles through the house, and providing a second exit in case of fire.

The main downstairs room would be heated by the Rayburn or similar with the upstairs and parts of the downstairs having minimal heating from a continous loop of large bore iron pipe through which hot water will circulate by gravity.

JohnB · Post by **JohnB** » 08 Jun 2013, 13:57

If it's a new build, why not do it to Passivhaus standards, so virtually no heating is needed? Use a cooker for cooking, and a heat source that can be started just on the coldest days when it's needed?

If there are currently two houses, why not create two? There's supposed to be a housing shortage, so why reduce the housing stock further? If the space is wanted for one household, design the layout so that as the parents get older, and the kids leave home, the large single house can be turned into two. The parents would have less expense and responsibility, and one of the kids could live next door, or they could let it to produce income, or provide a home for a carer if they need one.

woodburner · Post by **woodburner** » 08 Jun 2013, 19:13

Straw bales.

BritDownUnder · Post by **BritDownUnder** » 09 Jun 2013, 02:05

JohnB wrote:If it's a new build, why not do it to Passivhaus standards, so virtually no heating is needed? Use a cooker for cooking, and a heat source that can be started just on the coldest days when it's needed?

If there are currently two houses, why not create two? There's supposed to be a housing shortage, so why reduce the housing stock further? If the space is wanted for one household, design the layout so that as the parents get older, and the kids leave home, the large single house can be turned into two. The parents would have less expense and responsibility, and one of the kids could live next door, or they could let it to produce income, or provide a home for a carer if they need one.

A Passivhaus is something that I would like to do if I had the opportunity and I can definitely echo these comments. I believe that the cost of a normal house versus Passivhaus is about 10% extra for the Passivhaus though you will need a southerly aspect of course to make it happen.

When I was growing up we had a Rayburn with a large 1" bore copper pipe heating three radiators and a water tank. The circulation was done by gravity without a pump. However in summer you would need an alternative so solar hot water and space heating should be considered.

JohnB · Post by **JohnB** » 09 Jun 2013, 09:04

BritDownUnder wrote:...Passivhaus though you will need a southerly aspect of course to make it happen.

Do you?

BritDownUnder · Post by **BritDownUnder** » 09 Jun 2013, 10:21

JohnB wrote:
BritDownUnder wrote:...Passivhaus though you will need a southerly aspect of course to make it happen.
Do you?

Well... Northerly in this hemisphere.

Or are you thinking that you can collect the heat by means other than large windows such as solar collectors on the roof? I had not thought about that. I am guessing that it may be wandering away from the Passiv ideal.

sam_uk · Post by **sam_uk** » 09 Jun 2013, 11:51

It's possible to do straw bale to Passivehause standards. If they have the money for new build why not.
eg http://www.hausderzukunft.at/nw_pdf/fof ... _05_en.pdf

When we have burnt all the wood and completely deforested the country they will be pleased with it!

My approach to the question would be to rephrase it: How big a strawbale passivhaus can we afford? Then build that.

On size, just for a slightly different perspective, it's quite possible for two to live in a 8m x 3m boat, probably 4m x 2m x 3m total volume!

Double that would feel palatial to me now..

JohnB · Post by **JohnB** » 09 Jun 2013, 11:57

BritDownUnder wrote:Or are you thinking that you can collect the heat by means other than large windows such as solar collectors on the roof? I had not thought about that. I am guessing that it may be wandering away from the Passiv ideal.

That's what PassivHaus is all about, although Kenneal would be better able to go into the details.

JohnB · Post by **JohnB** » 09 Jun 2013, 12:03

sam_uk wrote:On size, just for a slightly different perspective, it's quite possible for two to live in a 8m x 3m space!

Double that would feel palatial to me now..

Funny you should say that. I've just posted this on the Tiny Houses UK Facebook page (that I just happen to run):

How a Family of 4 Lives in a 320 Sq. Ft. Home (Pretty Happily)

http://www.houselogic.com/blog/home-tho ... se-family/

sam_uk · Post by **sam_uk** » 09 Jun 2013, 12:10

Or are you thinking that you can collect the heat by means other than large windows such as solar collectors on the roof? I had not thought about that. I am guessing that it may be wandering away from the Passiv ideal.

As I understand it Passivhaus is a set of standards for energy efficiency.

So a passivhaus is just very energy efficient house. Beyond I don't see that adding solar collectors etc would effect the efficiency of the building.

There are a number of technologies and routes to creating a structure that conforms to passiv standards: http://en.wikipedia.org/wiki/Passive_ho ... nstruction

I'm quite interested in developing a 'kit' house constructed from sustainable UK timber, based on a opensource strawbale design.

My (pipe dream) business plan is;

1) Adapt this opensource straw bale plan so it's capable of meeting passivhaus; http://openarchitecturenetwork.org/node/641 or start afresh if need be. Spec out and find suppliers for windows heat exchangers etc

2) Get one past UK planning to set precedent

2) Make up wooden frames to form kit's from FSC UK timber

3) Sell the kits to self builders, Just add strawbales & windows etc..

4) Make millions, become the 'Barratt' of self built ecobuild houses

JohnB wrote:
How a Family of 4 Lives in a 320 Sq. Ft. Home (Pretty Happily)
http://www.houselogic.com/blog/home-tho ... se-family/

Standing headroom throughout. Now that's what I call luxury!

JohnB · Post by **JohnB** » 09 Jun 2013, 13:00

sam_uk wrote:Standing headroom throughout. Now that's what I call luxury!

That's one thing I've found I need. The roof in my van just scrapes my head at one end, and if it was an inch or two lower I would have found it very hard to live in for 4.5 years. Low ceilings are great though. My tiny home has a beamed ceiling where the bottom of the beams are a few inches above my head. They can be used for easy to reach storage, like CD and DVD shelves.

Post by **adam2** » 09 Jun 2013, 15:15

They are not keen on anything innvolving straw bales, fearing rot, mould, fire or vermin infestation.

Relatively conventional construction is favoured but with insulation considerably greater than the norm.

A footprint identical to the original would be favoured in order that foundations can be re-used to keep costs down.
It proposed that the ground floor be about 400mm higher above local ground level than the original dwelling in order to reduce flooding risk.
This will result in rather low ceilings, unless the planners will accept a slightly increased overall height.

They will be neighbours of other friends who built a house cheaply, and are particularly keen on concrete block internal walls for thermal mass, fire resistance, and better support for heavy items stored above.

Post by **kenneal - lagger** » 09 Jun 2013, 15:48

As far as I'm concerned every house should be designed for its own plot. Taking it to the extreme, if you have a house that is on a north slope with neighbours trees to the south you will be designing a very different house to one on a south slope with uninterrupted views. What should hold to every design though is optimal insulation standards and airtightness (Passivhaus standards for want of a better description).

I don't necessarily hold with the full MVHR spec required for Passivhaus because I'm a bit of a doomer, as most here will know, and I don't think that the spares will be available in the long or even medium term. I will be experimenting with a passive ventilation system with heat recovery, Ventive, in the eco hamlet that I am planning. It has no moving parts so will last indefinitely.

I would even advocate, if you have you own supply of wood, that passive stack ventilation be used with the penalty of an extra kilowatt or so of heat being required during the winter to replace the heat lost in the ventilation, assuming that is that the house is about 1200 sq ft. If you are planning a Rayburn or similar heating appliance in the kitchen this level of heat will be provided anyway.

If the house is to be occupied during the day, say if you have young children or work from home, I would say go for a heavyweight construction rather lightweight so that the sun's heat, and any extra heat sources, can be stored in the structure. Once such a structure is warmed for free during the summer it doesn't cost any extra to maintain that heat level during the winter but it will provide a huge bonus in 24 hour thermal comfort over a lightweight structure which, even if very well insulated, will have a tendency to cool quickly when the heat source is removed.

This preference for heavyweight structures is based on my own personal experience of having built and lived in both lightweight and heavyweight houses. As a bonus, the heavyweight house is far easier to keep cool and comfortable during the summer. That is assuming that we will have warm summers again in the future.

As far as size goes I would say about 1200 square feet is about optimal. With my nine house ecohamlet we are planning a separate two suite lodge for visitors to sleep in rather than every one having the cost of building, paying council tax on and heating that extra or spare bedroom. Our large four bedroom house would also offer extra accommodation and act as the hub building for the hamlet.

JohnB · Post by **JohnB** » 09 Jun 2013, 17:22

kenneal - lagger wrote:I will be experimenting with a passive ventilation system with heat recovery, Ventive, in the eco hamlet that I am planning. It has no moving parts so will last indefinitely.

Sorry to wander off topic a bit, but:

What's the cost for materials for a retro fit?
Is a separate unit installed for each room?
Can it be used with a wood stove (through a different flue)?

woodburner · Post by **woodburner** » 09 Jun 2013, 19:38

adam2 wrote:They are not keen on anything innvolving straw bales, fearing rot, mould, fire or vermin infestation.

All of which are available with other construction methods.