SAPs versus reality

[gc100]

Hi all,

 

I got my head into my SAPs calculations for the first time last night. Though I don't understand all of it I can basically see whats going on. However I had a bad surprise that they are predicting my year estimated heating/water costs will be £2560 a year. This got me looking at the u-values used and area m2 in the calculations. Firstly they used a u-value of 1.5 for the windows. We have a LOT of windows (56m2) mainly in 1 room and we've gone for triple glazed with a u-value or 0.9 so that should make a little difference to the calculations. Due to the fact our build is a conversion we've been a bit limited on how much insulation we can use especially on the floor (100mm). So I have a couple of questions:

• Firstly my main question is how close to reality are the yearly kwH heating/water calcs once build is completed?
• I see that have included the garage in the calculates as its part of the main build, but this of course is unheated (though insulated except for door) - is this normal? do they take into account its not a livable area in calcs?

 

Thanks

[Jeremy Harris]

I found that SAP over-estimated our heating energy use by a factor of about 1.5.  Whether that's just the way SAP works, or because we're in a relatively sheltered location, which tends to be a bit warmer than is typical for the area, I'm not sure.

[nod]

1 hour ago, JSHarris said:

I found that SAP over-estimated our heating energy use by a factor of about 1.5.  Whether that's just the way SAP works, or because we're in a relatively sheltered location, which tends to be a bit warmer than is typical for the area, I'm not sure.

One one there 

They over estimated ours also

Its  Rey difficult to guess 

Which in effect is what they are doing