Wall/whole house construction

[beelbeebub]

 

Ok, I'm just about to submit a planning app on bungalow with room in roof (so 1+1/2 story?).

I have a layout (see below) that has been created after consultation with the architect and a planner.  

The light blue sections are windows
Dark blue are entry/exit points like front door or patio doors(i.e. openings down to floor level)
The green rectangle shows the upstairs area

It is currently back with with the planner for comment.  If he gives the nod we'll work up the full application an go for it (fingers crossed).

Assuming the planner say go:

The building is ~9.5m by ~13m, aligned with the long axis (13m one) North/South.

The overall height is 5.5m from floor level.  The floor level will be just above local ground level (we will have to dig down but will dig down so that the new ground level is lower than the building floor level.

My budget is ~150k all in with me acting as the prime contractor.

As I am in a conservation area and an area of outstanding natural beauty the external look of the place will have to be "traditional" e.g clay tile roof (this has been specifically highlighted by the conservation officer) and render or brick exterior (i'd like to avoid brick on cost and personal taste grounds but am not dead against it if there is a compelling reason). That's not to say other external finishes like wood or metal are off limits, just we'd need a good reason for specifying them.

My question to the forum is:

WHAT SORT OF CONSTRUCTION SHOULD I GO FOR?  I'm talking about foundation, wall and roof construction.

I have my theory on the best construction, but I won't post it yet as I'm interested in other people's ideas, this is really a brainstorm session so I can get lots of view points to help me make a decision.

[djh]

I think you'll do better asking this question on the green building forum. JMHO.

[daftlad]

Tyres for the foundations (Earthship style)
Straw bales for the north, east and west walls.
Glass for the south facing wall.
Cob for the internal walls.
Oh and fit a masonry stove in the middle.
That is what I would do.
Sorry for banging on
laters

[dhaslam]

The layout of the building doesn't make the most of the sun for natural heat.  Perhaps the site dictated that the main axis of the house had tl run north south.   This will also cause problems for solar panels.  The best option is a long building facing south or perhaps a degree or two to west of south with shade over the south facing windows.  Also I would prefer a full two storey  house  or ordinary bungalow instead of dormer.  I think if I were building again I would use a lightweight insulating  block on the inside leaf of  the walls  and they would also help around the window and door openings.  Cavity should be as wide as building regulations permit.   I have used a cement,  white sand and lime mix on the outside  which avoids the need for exterior painting.   Brick is probably a good alternative but is not used in Ireland much now.     

[Amy]

Why not forward this to Amazon Nails and ask their people?
if you realy want an eco home, go ask a dedicated eco building forum. theres lots of wannabes there but also some real experts

[beelbeebub]

@djh:
good point, i'm cross posting this post, just as soon as I get registered!

@dhaslam:
You are right, the N/S axis the building is not great for solar gains. Unfortunately the site has dictated taht the roof ridge runs N/S.  This house will replace an existing cottage at the end of a "row" of buildings.  Every single building has a N/S ridge line, presumably because the road runs N/S so the houses were built parallel with the road.  Anyway as it's a conservation area and AoNB the planners have insisted that the ridge aligns with the other buildings.  I've tried to maximise the south aspect with the living areas all in the south and the living room and kitchen having very good exposure to the south and south west.  There is also a sunspace in the south west corner of the building to help offset any glazing losses from the large south and west windows in the kitchen and lounge.   Solar panels may have to be of the East/West type, again because of planning.  On the plus side summer overheating should be minimised 

The original plan was for a two story house but that was killed by the planners.  There is a height restriction as we are not allowed above the ridge line of the existing building (4.2m), so the choice is either a bungalow or to dig down a bit and try and get a little extra space in the roof. 

Digging down is not so bad as the site slopes, so we will be more digging into the side of the slope than digging down into the ground.

Ok so far we have had:

rammed earth/cob: daftlad
Lightweight block wide cavity wall rendered: dhaslam
straw bale:amy (I assumed since Amazon nails seem to specialize in that)

[EccentricAnomaly]

Presumably this is in the UK?  Anything special climatically?  How much sky can the south, west and east sides of the house see to the SE, S and SW?

What sort of U values and airtightness levels are you aiming for?  Any thoughts on how you're going to heat it?

Personally, I'm rather partial to timber frame of some sort at least partly because it gives a lot of choice with cladding and insulation.

[beelbeebub]

House will be in the southern part of the welsh borders (on the English side), so typical UK climate.

Sky wise, there's lots of trees around but it gets good sun this time of year.  As it's sunken down a bit the winter sun may be a bit lacking.  If it's causing a major problem we can always trim the tops off a few trees.

U value wise - I'm looking to get the walls to a really good standard, ideally 0.2 or less possibly into 0.1 terittory.  I think once you go below that you get the laws of diminishing returns.

I'm not 100% sure on most "green" technologies (we can go into that later) but one area I'm 100% convinced on is insulation.

And once you insulate to these levels the air change losses start to become bigger than the envelope losses so air tightness is also essential.

So we now have:

rammed earth/cob: daftlad
Lightweight block wide cavity wall rendered: dhaslam
straw bale:amy (I assumed since Amazon nails seem to specialize in that)
timber frame:Eccentric Anomaly

To paraphrase an old joke about economists:
Ask 10 green builders how to build a house and you'll get 11 different answers.

[EccentricAnomaly]

I like your answers w.r.t. insulation and airtightness.  The next paragraph would contain the letters MHRV, I guess.

[noelsquibb]

Ive done a couple of self builds and I would consider getting a specialist timber frame company to supply and erect.
'Room in the roof' joists would be part of this package.

My reasoning being that this goes up quickly, uses a renewable resource and most importantly, complies with all the building regs requirements. All your structural calcs are done, all the strapping and structural integrity taken care of and you get a warranty on the product. Your NHBC / Zurich / Architect or Building Surveyors 10 year warranty will be a straightforward process ( you need this if you plan to borrow against the property or sell it within 10 years )

Any outer wall you choose is then not part of the structure but can be as thick as you want to make it, as long as your founds can be shown to be capable of supporting it.

T/F construction is brilliant for 'first fixing' pipes and wires but you need to plan all wall support points and beef up as necessary before plasterboard.

You could be living in the building and still casting your cob walls if you find the project running into delays.

A 6" T/F stuffed with sheepwool, or more likely rockwool, seems to be acceptable for building regs U value with any outer skin adding to the total insulating effect. It doesent do the thermal mass thing so well though.

My patent cob mix could be cast against some dri-therm to form a cavity between the T/F and the cob, with stainless steel strapping securing the outer shutter to the T/F.  The cob mix I used was fresh dug subsoil mixed at 20 : 1 with OP cement, to create a product as strong as a thermalite block. I made it wet enough to behave like concrete whilst placing.
Obviously this mix is dependant on your subsoil. I did some cube tests to see what would happen and was really surprised with the crushing strength.

Air tightness and air movement requirements for building regs are difficult to reconcile but most vents seem to get closed when it gets colder, even the woodburner air vents 

Cost of my two builds was £30 k for the first T/F package and another £55k to complete ( built in 2002 )
Second one was T/F £35k  and another £65 k to complete ( built 2005).  That was for more or less the same 2200 sq ft house, so I saved on drawing up more plans and I could learn from my mistakes.  The second build was a more difficult site and all my friendly trades were expecting somewhat more for their efforts in '05.

A significant question is how Green can you afford to be ?  Standard builds, like I did, can cost you up to 50% less than high spec Green builds, because the whole housebuilding process in UK has evolved to allow continuity/ overlapping of trades and products. Step outside this process and you ensure an expensive can of worms, unless you are prepared to genuinely do it yourself, over a lengthy period and spend a lot of time at reclamation centres.

Bl*mey, I get all excited just thinking about it. Perhaps I'm ready to do another one ?

Preferably avoiding Architects, Planners and Building Inspectors, they can ruin the self build experience.

Noel

[beelbeebub]

@noelsquibb

The cob mixture idea is intriguing.  We will have to cut out a good chunk of clay to dig the house down.  It would be kind of elegant to reuse some of this.  The clay is potentially of very good quality -  there used to be a local brickworks not far from here that produced really excellent engineering bricks that were used in brick built railway viaducts several stories high.

Could you elaborate on the cob process and your experience with it?  Could it be used as a thin skim render (say 25mm think) onto a substrate?

As for how green can I afford to be.  Hummm a difficult question.  I wouldn't consider myself an eco warrior but on the other hand it seems as if our new houses are being built to woefully low standards.

I would like to build a house that uses low risk technologies that performs as well as it can do whilst not costing much more than a standard build.  I plan to achieve this by very careful working through and optimization of each element of the design.

So the first no brainer is extremely good insulation and this leads onto good air tightness and possibly heat recovery.

What i'm after is a construction method to assure me of:
1 good insulation
2 air tightness
3 comparable build cost comparable (but not neccesarily the same as) standard build
4 low risk

[billi]

I like these clay blocks

http://www.fbt.ie/

with  clay render

or here rammed earth/clay buildings

http://www.lehmtonerde.at/english/w2.html

Thermal mass is a good  buffer

Billi

[beelbeebub]

Hummmm, those clay locks seem interesting, does anyone have any experience with them?  I understand they are pretty much the standard in southern europe.

[rt29781]

The clay blocks are fairly common here in SW France.  They need perfectly flat foundations and more skill to lay than regular blocks.  They retail at about 1.8 euros each at the local Brico so they are twice the cost of ordinary cement blocks.  Very good insulating properties though.

[Amy]

i guess you cant avoid the planners, but you can get user friendly achiatects and hire your own build inspector

why dont you make a hybrid of straw, rendered with your clay and use the clay blocks for a thermal mass wall inside

hows about asking the local planning officer what he thinks stands the best chance of getting passed in your area?

you never know, he might be as kinky as us about eco build, so get him on side