Heat loss calcs?

[kudos1uk]

Hi,

I’m doing a kitchen extension which is brick and thermolite (100mm insulation) cavity walls with a glass roof (flowing from conservatory).

When I spoke to Building Control about this they told me on the phone I would need to show the house was no less efficient after the extension than before & that I could compensate with other measures like a new boiler.

No the inspector wants heat loss calculations, how can I go about getting these, can I work them out or do I need the services of a surveyor?

Many thanks.

 

[freddiemercurystwin]

Sounds like he is talking about SAP calcs, which can be requested if your glazing area exceeds 25% of the floor area. You can download the software I believe or you can pay someone with the software to do it for you.

 

[kudos1uk]

Yes I think your right she did mention 25% of the floor area. As the whole roof is glass its the same (even bigger due to pitch) than the floor.

 

[kudos1uk]

If anyone on here has the skills for this I'm happy to pay.

It's a simple 3.5m x 2.5m single story ext.

 

[^woody^]

You can download the software I believe or you can pay someone with the software to do it for you.

I thought that you had to be accredited to submit SAP calcs?

 

[freddiemercurystwin]

Maybe, I didn't think so, don't do them myself so not sure, or one of your leading questions?

 

[kudos1uk]

from experience is this going to pass?

Extension projecting 2.5m from the back of the house its 3.5 wide.

I intend to have thermolite on the inside and concrete bricks on the outside with a fully filled (batts) 100mm cavity, the floor will be solid with 100mm kingspan insulation. The roof and the reason for needing the calculation is all glass. Floor to ceiling (internal) 2.2m at front and 2.6m at back (closest to house)

No windows but a 1.8m x 2m patio door.

 

[^woody^]

Maybe, I didn't think so, don't do them myself so not sure, or one of your leading questions?

Not at all.

I was going to do some a couple of years back, but the calculations were headache worthy. I trialled some software and that was no better

Then I was told that I would need accreditation in any case, and this would cost a good few hundred £'s

 

[freddiemercurystwin]

A good SAP engineer will get it through, likely by increasing insulation elsewhere n the extension or property (eg the roof). Some will pay peanuts and get a crap service from their SAP engineer, I pay (probably in some peoples opinion) a fair whack (about £250) but I know he will get the calcs to work without having to go mad.

 

[kudos1uk]

I have already given her a before and after EPC, with a "A" rated boiler it gets through easy but she wont accept the EPC's and wants SAP calcs.

I think its all a bit daft after all I have already shown passes with EPC's

 

[freddiemercurystwin]

EPC's are not SAP calcs. They are different. You have not demonstrated compliance with the Regs with an EPC. SAP calcs are about 10 pages of gobbledygook.

@ woodchip I investigated getting the software myself a few years back and agree and frankly I would sooner have my teeth pulled than do SAP calcs. Though do not recall if accreditation is required or not.

 

[tony1851]

I thought that you had to be accredited to submit SAP calcs?

You don't have to be accredited; I've done a couple over the past 18 months, (by hand) but wouldn't do so again as Woody said they're a big headache.

Looking at the regs, if the 25% rule doesn't work, I don't think there is any legal requirement for an SAP calc. The wording just says 'one way of showing compliance would be etc etc'
In some instances, I've just added loft insulation in the house roof, and shown that the saving on that is > the additional heat loss from the extra glazing in the extension, and reasonable inspectors have accepted that.

 

[jeds]

Anybody can do SAP calcs. (well, you need to know what your doing but you know what I mean) The problem is the software. I've been using Elmhurst for years but recently dumped it because of the stupid cost. I've tried several alternatives but the cheaper ones are crap. Complete picture do a free version for checking etc. but you can't print any reports. I'm about to try EnergyDesignTools.co.uk which works by charging you for access time. I've got three houses on the drawing board at the mo so i'll buy a months worth (for fifty quid) and see how it goes. Otherwise it's a case of paying somebody else to do it.

 

[kudos1uk]

Thanks guys, after some pleading and based on the fact I have got my 70's semi upto an A rating they have agreed to accept the EPC's.