Calculating building heat loss for heat pumps.

alred

I will be starting a new build in the next few months. House is a 2-storey, masonary built of approx 3000ft. I plan to insulate to high levels - U-values of - walls 0.25, windows & doors 1.65, floor 0.20 and roof 0.13. I have calculated a heat loss (including air change) of approx 12kW. This is based on the following areas - Ground floor 171m2, Windows 62m2, Walls 270m2, Roof 171m2, Ventilation based on approx 1000 m3.

The problem I have is that 2 different heat pump companies have quoted an estimated heat loss of 21kW and 16kW respectively. Besides being 30%-60% more than my own calculation the figures differ by approx 30%.

From what I understand the correct sizing of a heat pump is imperative therefore these discrepancies concern me.

Any help???

Do-more

From my previous experiance, they are only using a "rule of thumb" to perform the calculations. My advice is to use an energy audit company such as http://iglooenergy.com/ to give you accurate figures and then submit these to your heat pump suppliers.

Boggle

Quick word of warning before you jump on the heat pump band wagon. I've been doing alot of research over the past 6 months and I have yet to meet anyone who has installed heat pumps and is even remotely satisfied with the results.
While I have seen people on here saying how great it is, I am also aware that there are alot of people plugging companies that hang around these boards.

Best advice is to find someone who is not affiliated with any of these companies and is satisfied with the results - having worked out the bills over a year or more. Find out who installed their system and contact that company.

I'm no heatpump expert mind you - all I am going on is what people have told me...

Do-more

Boggle wrote:

Quick word of warning before you jump on the heat pump band wagon. I've been doing alot of research over the past 6 months and I have yet to meet anyone who has installed heat pumps and is even remotely satisfied with the results.
While I have seen people on here saying how great it is, I am also aware that there are alot of people plugging companies that hang around these boards.

Best advice is to find someone who is not affiliated with any of these companies and is satisfied with the results - having worked out the bills over a year or more. Find out who installed their system and contact that company.

I'm no heatpump expert mind you - all I am going on is what people have told me...

Without putting it so directly I had already steered Alred in that direction with my post here Boggle http://www.boards.ie/vbulletin/showpost.php?p=51914989&postcount=2 As I said the heat pump business seems to attract more than it's fair share of "snake oil" merchants.

alred

Thanks for the info. I have been in touch with Iglooenergy and a couple of other energy auditors so well see what they can do for me.

Any advice on what to look for with these guys ie. what qualifications etc should they have.

babybuilder

hi alred

I will be starting a new build in the next few months. House is a 2-storey, masonary built of approx 3000ft. I plan to insulate to high levels - U-values of - walls 0.25, windows & doors 1.65, floor 0.20 and roof 0.13. I have calculated a heat loss (including air change) of approx 12kW. This is based on the following areas - Ground floor 171m2, Windows 62m2, Walls 270m2, Roof 171m2, Ventilation based on approx 1000 m3.

Just wondering how you sure are of your U-values? Have you included a margin of error? If it is a block build with cavity, error can range from 15 - 40 % of the projected U-values? Are you lining internally as well as cavity insulation? I would be interested in how you achieved these values

Do-more

alred wrote:

Thanks for the info. I have been in touch with Iglooenergy and a couple of other energy auditors so well see what they can do for me.

Any advice on what to look for with these guys ie. what qualifications etc should they have.

Energy auditors should all be much of a muchness, the heat loss is calculated by a computer program and once the data you provide them is good then should all come up with a similar figure. I think most use software complying with the UK Home Energy Rating standard.

To comply with the EU Energy Performance of Buildings Directive SEI are working towards introducing DEAP (Dwellings Energy Assessment Procedure) which should come into force in January. However a number of things have yet to be finalized so no one can audit to this procedure yet. From Jan '07 all new houses will have to be audited and issued with a Energy Label, my advise would be to negotiate a deal with whichever auditor you choose now that they issue the Energy label to you, when it becomes available, at a discount. (SEI's guide price is €100)

As for Energy consultant's that is a whole different kettle of fish! The problem, as I see it, is that there isn't the depth of real experiance with heat pumps in this country. I personally don't know of any independent source of practical advise on heatpumps, if anyone else does please post it here!

If you look at countries like Sweden where they install about 50,000 heat pumps a year their experiance has been very positive, using heatpumps of all types, air, ground, water and true geothermal. There is no reason why the same cannot be true in Ireland.

alred

Babybuilder.

The figures I'm quoting are best practice standards laid out by the Energy Savings Trust www.est.org.uk These are target values that I want to achieve. As far as the wall values go, I am dealing with a company in Galway who supply insulation solutions. They use EcoBead (polystyrene beads) for the cavity. With a 150mm cavity, they quote a u-value of 0.20. I'm not too sure how feasible this is (a 150mm cavity). They do claim to achieve a 100% cavity fill but I would be interested to hear views on this. I am still waiting for a quote for the entire house so can't say what the cost will be. Figuring in a 20% error margin, it should still achive 0.25.

Doors and window - talking to various suppliers and should be able to achieve approx 1.6 with not too much trouble - besides hurting the bank account.

Anyone with views on 150mm cavity?? Is this easy enough to do and will it cost much more than a standard 100mm?

babybuilder

Hi Alred
My sister has completed a build and they used a 150mm cavity. They fixed 60mm or 75mm kingspan to inner leave and then attached a further 40mm board over that. I know they found it difficult to get the right sized wall ties but did eventually get them. I'd say it probably added a fair sum to the overall cost.

Is there a possibilty that a completely filled cavity would allow for movement of moisture/water across the cavity? I'm sure I read that in a thread somewhere. Maybe check the sei website. There's talk of the present cavity size being increased in new regs so it is a v good idea. Regarding the U-values, my point is that by using the traditional double leaf system you will get most heat loss round windows and doors, at the wall plate area and thru the floor. It is thru poor building practices and not thru regs and guigelines which aspire for low U-values