Heat loss tests

[pc4107]

Has anyone done any practical tests on heat loss in a new house and compared the results to the BER rating???

[CCroly]

Are you asking if the heating energy figures shown by the DEAP spreadsheet are accurate?

If so, I’ve run a few tests against a constructed buildings actual heating bills and also detailed building simulations for the same building.

The DEAP spreadsheet result was within about 20% of the real results which is very accurate.

The electrical energy usage calculation seems a little wobbly.

The method is optimised for a building regulation compliant development through and using the same method for buildings that significantly improve on the building regulations will result in larger inaccuracies.

[VikingHouse]

Hi CCrowly, Did the house you tested use 20% more or less energy than you expected?

[CCroly]

The house measured used 20% more heating energy than the DEAP spread sheet calculated.

Only one years monitoring was used and I didn't check the degree days (weather) for that year against the degree days used in the method so the weather on the particular year of monitoring could explain a good part of the 20%. DEAP obviously makes assumptions about the hours of occupation of the house etc so taking all of that into account I would say the DEAP figure is quite accurate.

-------o----------
This is not related to the question but may be of interest. A little messing with the DEAP sheet seems to show that under floor heating Uses 36% more heating energy than radiators (according to the method)

So this means that a heat pump with under floor heating generates 4% more carbon than a good condensing gas boiler with radiators. (I wonder if SEI still giving out heat pump grants for heat pumps in housing where natural gas is availible?)

For ballance, if the home owner is intending to use under floor heating anyway, then the heat pump is shown to be about 15% better than a gas boiler.

[pc4107]

Thanks for the info, i was thinking more along the lines of measuring the actual change in temp once the heating has been switched off over a stated time and comparing it to what would be expected according to DEAP?

[VikingHouse]

This is not related to the question but may be of interest. A little messing with the DEAP sheet seems to show that under floor heating Uses 36% more heating energy than radiators

I would agree with this comment as Swedish research shows that you get as much heatloss through the floor as you get from the roof due to convection.
In order to get the best results from your UF heating you need to insulate your floor to Passive levels (30cms) for all instillations. Because of the external proximity of the UF heating pipes in the floor the level of floor insulation becomes even more important.

[CCroly]

Thanks for the info, i was thinking more along the lines of measuring the actual change in temp once the heating has been switched off over a stated time and comparing it to what would be expected according to DEAP?

DEAP doesn't give you that kind of information? It calculates the heat loss at one point in time and then multiplies it by a correction factor to work out the heating enegy for the full year. (A simplification on my part, but you get the idea)

The information you are after has to come from a dynamic simulaiton or real measurements.

[CCroly]

Time 2002 Regs 2008 Regs
18 22.001 22.001
19 20.5705 21.01152
20 19.61164 20.23137
21 18.82 19.55424
22 18.14565 18.95247
23 17.6214 18.47532
24 17.20094 18.08653
1 16.91152 17.80435
2 16.6911 17.58105
3 16.37712 17.25536
4 15.95474 16.82749
5 15.47272 16.3225
6 15.30607 16.11037
7 15.01295 15.81822
8 14.68589 15.4902
9 15.02192 15.69318

[CCroly]

I pressed return by accident on that one!

It is the simulation results for a typical living room when the heating is turned off at 6pm on a typical winter night.

Best viewed in graph form and I can't post graphs to the forum, so if you are interested, copy into excel and graph it.

The first column is the time, (6pm till 9am)
The second is the temperture after the heating is turend off (if insulated to the 2002 regs)
And the final column is the same thing but with (2008 regs)

Pc4107, If you tell us why you are interested in this information, we might be able to give more meaningfull help.

[Adrian Hennessy]

Why are people assuming some kind of co-relation between DEAP and actual heating figures?? DEAP is a standardised calculation method and never at any stage purports to be any different.... it quite clearly assumes occupancy based on floor area and not actual occupancy so it cant possible be used to predict actual heating factors....

the BER is standardised so buildings can be assessed in comparision with each other, it is not designed to be a singular certification for individual buildings and situations....

[CCroly]

Adrian

The reason that people are assuming that DEAP gives an indication of the buildings heating energy use is probably because its results seem to be quite accurate. (at least as accurate as any other method if the house is build to building reg standards)

Note that DEAP does even suggest running costs on the results sheet which would be very inappropriate if they were very inaccurate.

You are correct to point out that it was never intended as an energy usage calculator though but look at the alternative methods of calculating energy usage for domestic buildings.

The traditional method is the degree day method which is even more wobbly than the method used by DEAP and also assumes average internal gains.

Dynamic simulation will give an accurate result but occupant behaviour in a house tends to be quite erratic and varied and as a house is a small building these user effects make up a large proportion of the total load, making the accurate simulation results, not much more accurate than the DEAP figures, unless the building is very large or deviates significantly from the building regulation values.

[Adrian Hennessy]

thats interesting CCroly... i hadnt realised other methods were (probably) less accurate than DEAP....

what tests did you run on your example?? is there any tweaking that can be done to DEAP that may allow for more accurate results??? purely for advisory purposes of course and not BER.....