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Recently had planning permission for a self build. Fortunately I avoided the need to comply with CSH, but that doesn’t mean I don’t want a well built and well insulated home.
I’ve had a SAP calculation done by the local building control department, but got the impression that the guy doing the calc was not that switched on…..so I’ve done some reading on the net and have some questions…specifically regarding the nominal dwelling and limiting u-values….
I’m looking to achieve a SAP rating of B, and had hoped to achieve without the use of renewable (I’ve every intention of installing solar) but the calc suggests that I need solar to scrape a B rating….I could really do with discussing the finer points?
If you feel you can help, please email me. Address in profile.
Thanks
Stoner to the forum please.
(if you ask nicely he'll show you his pellet auger 😉 )
*poof*
Your SAP rating takes into account your energy consumption on a volume/area basis.
I did all my own u-value calcs from specs and supplied them to a tame SAP assesor. She pumped my numbers into her calculator and gave me a cert for £100 (and EPC) for my (private company, not LA) building control guy.
You dont necc* need renewable to get B, but you need to do very well in other areas to make up for itand its very difficult as far as I can tell if the calc is done with mean assumptions on air pressure etc. And Air pressure test would cost a bit.
Dont sweat the SAP too much. I got a rating of D63 and met all reg requirements and I have biomass heating, solar panels and tons of insulation. But mines a barn conversion so an air pressure test would probably be crap so went for assumed values.
My enviro impact on the other hand is A93.
* actually you probably need at least solar water
Damn that was quick....
Stoner - I've come across some of your posts so understand you've built your own, but not really had a good look....I was just looking at your profile to get myself up to date...
Any help/advice appreciated....
ponty - pm me.
As Ive just finished a self build and come out the other side on budget, on time with no problems and learning a lot Im happy to pass on anything Ive picked up on the way.
Its also opened me up to a whole world of renewable energy stuff which is interesting me and Im thinking I might get a bit more involved in it as a hobby/part time job in the future.
<where's that auger dammit!>
😉
*mwah*
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Ahhhhhhhh.......
My SAP calc came back at at B82 (With 5m2 of solar and 200 litre storage 50mm insulation) but I have some queries....
From what I understand they take my build dimensions/areas/volumes etc and key into a program with U values that I'm going to built to and it compares the energy usage with a nominal dwelling.
My question is whether the nominal dwelling is just that, a nominal dwelling of the same size with average glazing or if it should assume the same glazed area as the actual build? In the calcs, the nominal dwelling has 20m2 less glazing than the build which means I'm being penalised as the glazing U value is much worse than a wall!
Would you mind checking if the TER and DER sheets in the SAP calc have the same glazed area?
I also have a question over the U value that is being used for the roof construction. The roof is a room in roof construction, with insulation between the rafters. From what I can find online, a U value of 0.2 should be used in the TER, but the calc is using 0.16 which is for a pitched roof with insulation at ceiling height (joists)?
I'd really appreciate if i could have a look at your SAP calcs? It might answer a lot of my questions.
Ta
Lovely auger.....
Was typing away as you posted, thanks for the offer....I'll be in touch (might be later in week as I'm away with work for a few days).
Could do with all the help I can find when it comes to coming in on budget!
Ta
Bit of a threadjack, but I'm seriously considering self build.
Assuming land and house already paid for, with me, BIL, FIL (carpenter/builder), step-dad (retired house builder) and mate (plumber) doing most of the work, what's the likely cost of actually building the place? Approx 175-200m2 footprint, 1.5 storey.
If you PM me, I'll send you a copy of part L tomorrow if you want it.
the total m2 is the same between the DER and TER, but the allocated surface area for different construction definitions differs. The TER is based on assumed levels of glazing etc, the DER is on actual. SO yes if you're building a glass carbuncle ( 😉 ) you will be penalised as windows u values are rubbish compared to walls.
My roof is partially "room in roof" (short pitched section) and then flat ceiling. My pitched section I built with 50mm xtratherm with a 10mm silver tlx membrane. Gives me a U of 0.23.
300mm of mineral wool on a ceiling gives 0.13.
so your room in roof construction is going to penalise you heavily. Im not a huge fan of them, even for barn conversion because of this (and bridging effect when people plasterboard between the rafters - my tlx crosses the rafters before overboarding reducing bridging losses).
Stoner will be better placed to answer, but you can make big savings doing the work yourself, but it all comes down to specification.....first the construction and then once you start spending on fitting out
I'm going to project manage,most likely with one contractor for groundworks, another for shell, window company fitting windows and a roofer.....after that I can get more involved, subbing out electrics and plumbing....I'm hoping to come in at around £850m2.
There are big regional differences...I'm in S.Wales where labour is cheaper, but as you'll be doing much of the work yourself....
just remmebered I did these and hosted them for my BC guy:
my roof
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and calcs
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Stoner....struggled with planning for height (between two old 1940's low pitched bungalows, just 3.8m to ridge!). So ended up with a mostly single storey build with a master bedroom, en-suite and study above a garage...
Ok, so it looks as if the nominal dwelling U's are correct and its up to me to find actual build U's that better...
Thanks
OX - get yourself a subscription to http://www.selfbuildanddesign.com/ and http://www.self-build.co.uk/ in the back of one or both is a ready reckoner for costings.
My barn conversion was about 3,000ft for £250k = £83psf but that includes £7k for biomass over and above an equivalent oil system. I also got a cheque for £18k back from the VAT man (which will cover landscaping and solar) so that would make it £77.
I "jobbed" 4 days a week on site and many weekends and paid a builder mate (who did all the hard stuff) to do 5 days a week as well as one other guy doing bricking and plastering.
look at tlx - bloody expensive but should help your Us. Are you over boarding the rafters or in betweening?
http://www.builddeskonline.com/sw61061.asp
I used the demo a bit - great for playing with different constructions for targeted U-values.
Do also remember that insulation is relatively cheap in the overall of a build - worth chucking all you can, as effectively as you can and being as fussy as over airtightness. You will save the cash / hassle of doing this.
that reminds me, I used an online sap calc programme at knauf insulation. then the f******s packaged the product off to another provider who put it behind a paywall.
http://www.energydesigntools.co.uk/
Im not a fan of giving them any money, but if you dont find a free source of sap calcs, then this one was easy to use.
Air tests aren't that expensive!
Ponty/Stoner - Cheers!
for a £100 pound certificate that doesnt mean much they are 😉
Isn't it a buildings reg requirement now on all new dwellings.