HighlandHopeful Posted January 29 Posted January 29 Hello all, I have a trial for Elmhurst's SAP10 (1 week into the 2 weeks) and had a great time at the weekend inputting all my area info, U-values, construction type and openings sizes and picked our intended MVHR and ASHP from the inbuilt database. The only defaults I left in were a) I left in the default for thermal bridging which includes a Y-value of 0.200 b) I let it tell me the kappa values for the thermal mass of the walls/floors/roof which then calculates the thermal mass value. But then, I pressed the magic button to calculate everything and...... got a SAP score of 55D and energy/CO2 70% WORSE than the target property. Obviously terrible. Does anyone have experience with Elmhurst's SAP10? Is it that I shouldn't have left the defaults in? But why are they defaults if they are so inappropriate? The house is one story, 1-bed, pitch roof, 81sqm, u-values roof 0.11, wall 0.13, floor 0.15, UFH (yes you won me over!), ASHP (heating and DHW), MVHR - I'm not saying it is perfect, but how is the SAP so so so low and how is it so much worse than the target property? We only have one heat source, in case that makes a difference. I have the SAP of my niece's 4-bed house she is currently building which has higher U-values than us and only double glazed, and the energy and heat demand of our 1-bed is almost twice that of the 4-bed so something is obviously very wrong. What's weird is that I've tweaked loads of things to see what it is that is making it so bad, e.g. changing the floor area, reducing the openings, speccing a different heat source, and it only changes the SAP like 2-3 points in either direction. So is it the thermal bridging and the kappa values (i.e. the things I left as default) that make such a difference and I shouldn't have left in the defaults? Just wondering if anyone has experience with Elmhurst's SAP10 or other resources/software that does SAP that can shed any light. I have been trying to get in touch with Elmhurst but not hearing back yet so thought I'd see if any of you had any thoughts in the meantime. Thanks!
JohnMo Posted January 29 Posted January 29 Did you do the print out? It should give you model for your design and build regs design so you can compare. What did you put in for airtightness at 50 Pa? What did it give you as an infiltration rate? Would compare target house with your inputs, check your inputs are not strange. Would also add another 50mm insulation to the floor. Check MVHR inputs, different duct types can make a big difference in efficiency etc. Heating controls make difference, can you select pure weather compensation?
ADLIan Posted January 29 Posted January 29 SAP 10, it's inputs and their relationships are very complex. You need to read and understand the SAP 10 guidance document (nearly 200 pages of fun) and the relevant SAP Conventions document - available from the BRE.
HighlandHopeful Posted January 29 Author Posted January 29 1 hour ago, ADLIan said: SAP 10, it's inputs and their relationships are very complex. You need to read and understand the SAP 10 guidance document (nearly 200 pages of fun) and the relevant SAP Conventions document - available from the BRE. hi, thanks for your reply. I read the guidance document manual as I went along and was v dilligent, the only thing I didn't change was kappa for thermal mass and the thermal bridging. I'm going to work out how to do those for my design and see if it helps. Did you do your own SAP assessment using a software, did you modify the thermal mass/thermal bridging inputs? Thanks.
ADLIan Posted January 29 Posted January 29 I was a SAP assessor, now retired. Yes you do have to input project specific data - the defaults will really screw you over!
HighlandHopeful Posted January 29 Author Posted January 29 2 hours ago, ADLIan said: I was a SAP assessor, now retired. Yes you do have to input project specific data - the defaults will really screw you over! 😃 thank you! ok off I go to get some Psi values (sigh)
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