No, the W/m2 figure is a peak figure - it's the maximum demand that you need to meet in the depths of winter.

Your calculation gives a yearly average, which is of course much lower, since you don't use heating in the summer.

There's no easy way to work out one from the other. It depends on the climate and window area etc etc

By the way, to give some context for "highly speced european houses have a figure around 25 watts/m2" - the limit for a passivhaus is 10 W/m2

Max total overall PRIMARY energy use for passivhaus is 120 kWh/m2/y

Max space heat demand - DELIVERED 15 kWh/m2/y

To calculate the Heat Load ( w/m2 power of your boiler/heat pump ) you need
U * A * Delta T

U= whole building U Value
A = Total area of exposed elements
Delta T on coldest day ( 30 year avg ) , depends on where you are Dublin 22 degrees . ( 20 degrees indoor - 2 external)

Passive house max - 10 w/m2

Thanks all, my SAP calc is not easy to understand! maybe deliberate policy.
Tony, I can remember discussing with you some time ago the wall construction designed by by architect. I think it was 100mm dense block- empty cavity 110mm-insulating block 100mm-Knauff board for dry line and wet plaster (I think) anyway the construction method gave my walls a U value of .33 and I was not happy with it for a new build. You also mentioned that his design would be draughty (see I do listen). To cut a long story short I then approached my BCO and as we are deemed to be a very exposed part of the country (and we are a little stuck in our ways) down here on the west coast of Wales planning like the block construction etc and I could not have less than 50mm air gap in my cavity. So this meant with my current plans and permission etc I could only fit 60mm insulation (no knauff board)which I did. This then gave me a U value of .26, not brilliant but better. Then I decided that if my walls could not improve greatly within my budget I would look at windows. My SAP calc and architect had windows at 1.8 but the windows I am fitting are 1.3. so again, not PH levels but better than the designed windows. Also my loft insulation was shown as 300mm glass wool and I have purchased loads of this (on offer) in preperation. My loft was shown as .14 for 300mm but I will fit about 540mm if I can without causing any problems? I am unsure what value this will give me but fairly low I would imagine. So I am trying to do my bit and reduce my energy usage if possible?
My original plan also had a log burner in the front room with no back boiler, this now has a back boiler fitted to improve things again. I was also possibly going to fit oil CH but I feel this is the wrong move for times ahead. I am now considering a pellet boiler instead. I have also looked into trying to keep the house air tight and minimise draughts. I am hanging my joist instead of fitting into the cavity and I have fitted a dedicated air supply to my log burner that will be room sealed so I am trying to build as well as my budget allows unless all you lovely folk out there will help for free? I know this is a silly question but my original SAP calc showed my house as-
Energy efficiency rating 78
Enviromental impact (CO2) rating 75

Do you think the changes I have made and will make will greatly improve these figures? Ball park estimates appreciated as I am in band C for both at the moment and that makes me sad so I hope with the changes I have made and will make I might make a B

I hope that this post makes sense as I am on very strong pain killers at the moment for a throat infection and I am not quite in the room if you know what I mean?
Gusty.

Tony, you would if you couldnt eat for 4 days, even soup was a no no. A cup of tea took 60 small sips!
Better today though, on the road to recovery