heat loss calculations

[Joeboy]

more details (I shouldhave had these at the start!

floor area is about 218 square meters (2350 sqr feet)

high cealings, 2.1m (10ft) downstairs, 2.75m (9ft) upstairs

mix of single and double glazing

I guess my shock is, that I thought with good underfloor/loft/ewi I'd be able to bring the numbers right down low

That is quite a property
I guess your 218 square metres is just the ground floor size?
From a heating calculation point of view, think you need to consider upstairs & downstairs separately, so more like 400 square metres, which maybe explains the high heat loss, with high ceilings too - good luck!

I didn't add it all up, but at 400mtrs and 19kW, seems quite close to what we'd expect going on the info posted by other members. I'd defo start with as much loft insulation as I could without killing airflow at the eaves. Fast and effective and since you've recently bought, not too expensive. What roof is on the conservatory?

[spread-tee]

I've just done a few back of envelope calcs using the old rule of thumb and come up with
Study 3771BThU/Hr
Lounge 14,405 BThU/Hr
Sitting room 11,638BThu/Hr

Which sounds reasonable to me from days past FYI the formular I use is Volume of room in M3 *35.3 to get CuFT *5 to get heat requirement.in BThU/Hr
Divide those numbers by 3400 to get the room requirement in kW.

That method of calculating is a bit rough and ready, but as I said earlier when we started using the Mears calculator there was not much difference. The Mears though did have an adjustable scale to make allowances for extra large windows or a room with two or more outside walls. Basically 10% was added in each case. Give it a try if you have a couple of hours to spare, it will at least get you near the ballpark.

Desp

[knighty]

That is quite a property
I guess your 218 square metres is just the ground floor size?
From a heating calculation point of view, think you need to consider upstairs & downstairs separately, so more like 400 square metres, which maybe explains the high heat loss, with high ceilings too - good luck!

I didn't add it all up, but at 400mtrs and 19kW, seems quite close to what we'd expect going on the info posted by other members. I'd defo start with as much loft insulation as I could without killing airflow at the eaves. Fast and effective and since you've recently bought, not too expensive. What roof is on the conservatory?
[/quote]



Conservatory roof is polycarbonate, that twin wall stuff that looks like it has loads of tubes in it (can't remmeber the name of it)

We're going to take the conservatory down and do away with it, it's knackered anyway - there's a small retaining wall in the garden so you have a small raised garden at the back of the house then go down some steps to therest of the garden.... retaining wall is knackered so the ground has moved a bit and the conservatory has twisted/moved a bit.

I'm keen to insulate the loft asap... but need to rewire and replumb the place so would rather do that first, save putting insulation down to take it up again

plan is (roughly) to power through this winter then sort the heating out in the summer where we'll be ok without it while it's done

[Joeboy]

If you included the poly roof and conservatory in your calc. It would pull the end result down?

We like photos!

[Stan]

Hi Knighty
I guess that in your plans above you meant to put ceiling height as 3.1m(10ft) and not 2.1m(10ft).

[knighty]

Hi Knighty
I guess that in your plans above you meant to put ceiling height as 3.1m(10ft) and not 2.1m(10ft).

my bad, that was a typo here, hights in heatpunk were right :-)

[Stinsy]

more details (I shouldhave had these at the start!

floor area is about 218 square meters (2350 sqr feet)

high cealings, 2.1m (10ft) downstairs, 2.75m (9ft) upstairs

mix of single and double glazing

I guess my shock is, that I thought with good underfloor/loft/ewi I'd be able to bring the numbers right down low

Mystery solved! Your house is mahoosive!

The rough rule of thumb is 75W/m² for prewar houses, 30W/m² for new-builds, and 20w/m² or lower for modern eco homes or houses that've had insulation upgraded substantially. Obviously a proper set of heat-loss calcs will be way more accurate.

A typical 3-bed semi is 100m² so if it is a new-build it's heat demand will be 3kW. Therefore a 7kW HP will be plenty for the coldest day and do DHW as well.

Your house is c. 400m² and you need to add 25% for the 10ft ceilings and 12.5% for the 9ft ones. So that gives 36kW if it is in original condition. However if you do a full upgrade (walls, windows, roof, doors) to modern standards you should be able to get it down to 10-12kW.

It comes down to how much you're willing to spend and how much disruption you're willing to endure in order to achieve your target heatloss...

[knighty]

Plan is to get the heat loss as low as possible so we can cover the heating with solar+batteries most of the time

Would like to get the bills down low before we get old!

I like the idea of ewi... but that's a really big job and I'm guessing crazy expensive


At least I know what the numbers are like right now and what to aim for... I was shocked by the high numbers and assumed I'd messed up somewhere

[Stinsy]

Plan is to get the heat loss as low as possible so we can cover the heating with solar+batteries most of the time

Would like to get the bills down low before we get old!

I like the idea of ewi... but that's a really big job and I'm guessing crazy expensive


At least I know what the numbers are like right now and what to aim for... I was shocked by the high numbers and assumed I'd messed up somewhere

EWI depends mainly on the style of the building. You generally end up with a very-modern looking rendered box. No problem if it is super-ugly to start with, but a bit undignified if it is a beautiful Victorian creation...

However EWI keeps the mass within the thermal envelope and therefore the thermal mass helps to modulate temperatures.

[spread-tee]

Plan is to get the heat loss as low as possible so we can cover the heating with solar+batteries most of the time

Would like to get the bills down low before we get old!

I like the idea of ewi... but that's a really big job and I'm guessing crazy expensive


At least I know what the numbers are like right now and what to aim for... I was shocked by the high numbers and assumed I'd messed up somewhere

EWI is not that expensive if you are prepared to DIY most of it, IE prepping the walls, sticking the insulation, fixing the beads, moving any down pipes and extending cills etc. All of which can be done bit by bit. Slightly more challenging is the basecoats and mesh, but it doesn't have to be perfect, then you could get a good spread in to patch up the basecoats and spread to top Silicone render (which is quite tricky) or at least bloody messy.
That is assuming you are OK with a plain rendered finish, brick slips and what-not are expensive and time consuming, but if you have any experience of tiling your bathroom, you're halfway there.

Quite a lot of our house is now covered in EWI and the difference is just light years from how it used to be, me and a mate of mine did 80 m2 ish in 6 days IIRC.

Desp