Dave Jones

The heatloss calculator on the same site is excellent

well spotted, its internal but the calc had it wrong way.

the titan wet/dry from screwfix is a bargain. https://www.screwfix.com/p/titan-ttb774vac-1300w-16ltr-wet-dry-vacuum-220-240v/826kh

running the values for my solid wall buildup (225 brick,100mm celotex, plasterboard, plaster) through the calculator using -10c external 26c internal still puts the dew point well inside the insulation so I don't think any air gaps between the bricks and insulation is needed.

accumulater is essential depending on your useage. 2 showers happening and the dishwasher turns on for example will result in a dribble.

disagree. as long as its insulated its superior. Just same as internal walls not freezing as they are insulated etc

use marxox blocks under the joining walls. These shed builds never fail to amaze.

is that a cold roof or a warm roof ?

standard gulley pot would be ideal as they have an integral trap to catch any rogue items that may accidentally fall in, also stops the smell. screwfix/toolstation do them.

sheer daylight robbery. at £250 a day ask them how long they will be onsite for, a month ?

65k to stand up some timber ? couple days work tops for a crew and crane. sounds bad but then timber frames are a rip off. Unless you planning to completely finish the build in 4-6 months I fail to see the benefit of paying over the odds for TF as its quick to erect then losing all the expensive gained time anyway. See it all the time locally, normally pushed by clueless architects onto unaware clients thinking it will speed everything up.

no its slower and cheaper.

it wont be the beam is insulated and air is a better insulator than wet ground like a traditional slab. B & B every time for me, fast, accurate, less labour, better for environment.

you need to get your plans properly QS'd, estimators.com are pretty reasonable. email them your plans and elevations you will get back a price down to every last nail. It wont have foundations or steelwork unless you supply the SE spec as well but you will have a guide on what it will actually cost to then discuss with a builder.

dont take too much notice of EPC its junk science at least at the moment where electric is penalised. Hire in a micro digger and tracked dumper (both go through a front door) for a weekend and you'll have it done. 300mm of XPS insulation would be great. 150/200mm hardcore+sand blinding+ 150/200 conc then screed on top. Just work down from FFL to see your max depth, careful not to smash any drains. 100mm pipe spacing allows underfloor flow temp to run lower and much more efficiency for the small extra cost of a bit more pipe. Dont bother with zoning the underfloor it just reduces efficiency.

put a fan (normal desktop 12" will do) in a doorway/window and seal around it to the frame with bin bags to depressurize the house then go draught hunting.

56k will buy an awful lot of brickwork. Golden rule to remember 99% of architects are clueless on how to build anything. They are good at milking clients though. For example look at any of the window openings your architect has drawn and i guarantee you none of them will work brick. If they had a clue how to build anything they would design them to be built.

lose the timber frame and cladding and go traditional brick/block will save min £300m2, pay an SE to give you a foundation spec that can be priced. Have your plans QS'd to see the actual material costs.

buildup doesnt matter you are digging down. 25mm isnt going to do much, 50% (even believing that figure) loss means you need double the heat output. Madness.

if the stud is already in I wouldn't worry about it.

all that info is great but not really of any use. What is your heat loss calculation ?

how are you using that tape to seal against the wall junction ? It's not an approved method its a bodge. Use a real VCL and seal the roof properly, that means no cuts and sealed onto the internal walls.

make a simple mitre box out of scrap timber with a slot in it to guide the saw, dead straight cuts every time.

no such thing as a hybrid roof. warm roof requires a real VCL layer brought down onto the walls and not punctured by downlighters etc. Taping insulation IS NOT a VCL and wont work especially in high moisture areas like kitchens.

UK alternative will be less than half what you have been quoted by rational. R7 Flush Casement triple glazed (very nice window) whole frame u value of 0.84