Bit of heat loss??

L driver

Hello,
Doing a few figures, might not be too accurate, getting fabric heatloss results of between 1.5 and 1.8W/Km2 depending on inputs to DEAP and want to know if these seem right for a new build. Could someone put it into layman terms please. I get a bit lost when it comes to figures.:o

L driver

Hello,
Sorry, gone through it again and coming up with 0.9 W/m2 had omitted some data. Is this a more important figure than the final rating, like B3 or A1, because with different inputs for different fuels etc the final rating changes quite a bit. Mods feel free to move this but I think it is not a specific BER technical question. Any help would be welcome.

sinnerboy

The figure you refer to here is aka the "Whole Building U Value" i.e. averaged out over the various elements.

Simple example ( leaving thermal bridging out for simplicity ) suppose

Walls/roof/Ground floor are all 0.2 W/m2K and = 75% surface area
Windows are all 1.8 W/m2K and = 25% surface area

Then (( 0.2 X 75 ) + (1.8 X 25 ) ) / 100 = 0.6 Whole Building U Value

Now taking thermal bridging into account , DEAP takes the factor entered and multiplies it over the area of all elements to reduce ( i.e. numerically increase ) the Whole Building U Value.

If your getting a result of 0.9 then yes you are playing with the kind of elemental U Values for a new build.

However - all of the above relate to fabric heat loss alone. Just as significant in terms of energy efficiency and occupant comfort is ventilation losses.

On the "plus" side solar gains can and should be optimised.

And lastly - how to provide heat / what fuel do we use?

Simplified DEAP .

But really you are best advised to hire an SEAI registered assessor to "play the numbers" for you. They don't cost much and a good one will repay his/her fee by a huge multiple.

L driver

Hello,
Thanks Sinnerboy for a clear responce. Yes I have a BER registered guy, but in old job it was compulsory to do the ber course so I have the software and I'd rather be playing around with it than watching soaps/football until the evenings lengthen. A good point in relation to DEAP is how the air tightness level is weighted in the software. People think a bit of fibreglass in a hole makes it air tight in this country! Anyway when I adjusted my ventilation figures the fabric u value changes as well. Can I from this figure, elemental u value, and the area work out the size of my heating needs, I am doing this for my own interest/education and to see how I compare to heating companies as each one is specing a diff size unit and to compare with my BER assessor. My overall W/Km2 is now 0.8, this may not be exact but for the sake of calculations and furthering my learning it will suffice.

sinnerboy

The DEAP manual advises on boiler sizing

L driver

Thanks again Sinnerboy,
Give a man a fish.... teach a man how to fish:o In relation to dT do we assume -10 as normal for the next few winters or am I looking at it wrong, also the kW for DHW can we be more precise than 2 to 4? You are probably going to tell me it is in the manual.....

L driver

Hello again..
I make it that 1.2 kW is enough to heat a 500ltr store to 50+c? And that is from cold.