New Build Heating Design

lkkev80

We have submitted a planning application for a new 2 storey house....we are being optimistic regarding the planning (might well be brought back to earth quickly in the next few weeks!) and thinking of next steps. One of the issues we are thinking about is design of the heating and hot water requirements / system.

The architect has designed the house with passive principles in mind .... lots of glazing / living areas on the south and limited glazing on the North. As we will be subject to the new planning regs we will have good insulation on floors, walls, roof etc and have outlined to the architect the need to have proper design for thermal bridging and air tightness. I plan on putting a requirement of <1 ach for a.t. in the tender documents.

One aspect we are not sure of is the design of the heating / hot water requirements....the architect said we can rely on the plumber appointed by the main contractor or hire an M&E engineer but obviously there is a cost to this. Would be interested to hear the experience of others...is an M&E engineer necessary? The architect advised this would cost around €2k...is this other people experience?

Calahonda52

When you say PH principles in mind: it's either to passive standard or not.
I don't mean CERTIFIED.

What heating system have you in mind, against what thermal loading?
How is the renewable requirement being met in the planning?

The HW design is not hard, you cannot, I repeat cannot, let a plumber design, install and commission a heat pump unless he is certified to do so, its a lot more than qualpex and PTFE tape.
I think you will have issue with an ach target in the tender without a detailed plan for checking it along the build route.
What would the tender say if it was not met?

Are you having MVHR?

Have you provided for brise soleil ?

lkkev80

Thanks for the reply. I am no building expert hence my use of an architect and request for information on what other professionals to use.
We don't plan on it being passive, we will not set the air tightness target to <0.6ach and the u values for the walls etc will be based on the new building regs rather than passive requirements. The brief to the architect was to design so as to take account of passive solar gain and to keep the design simple so as to minimise comeplexity with air tightness and thermal bridging.
Heating system I have in mind is ASHP with radiators but here is where we will need good advise...I prefer rads to reduce the cost of the heating system (am I correct that it is cheaper?) but obviously we need the right number of rads (thermal loading)....my fear with getting the wrong advise (ie somebody using a simple calculator that can be found on Internet for each room) is that they would say it is not possible to use the ashp with rads or else just plaster every free wall with big rads.
In the planning we have put PV panels on the roof facing ssw.
Yes we plan on having mvhr, no plan for brise soleil.

OK so good to know we should not let a plumber do it. So would you recommend working with an M&E engineer?
Thanks

Calahonda52

1. building new now just to the current building regs is a wasted opportunity. period.
2. Reduce the footprint of the house to make it work within budget.
3. Its the full LCCA that you need to look at
4. maxing passive solar gain without considering the need to fit brise soleil is recipe for summer overheating.
5. how is he he achieving simplicity re air tightness?
6. i cant comment on the pricing but rads will work, research the delta T concept of rad design and then assume a heat pump flow and return temperature profile.
7. Rads will be bigger yes.
8. The higher the temperature lift for the HP the lower the COP, hence UFH, properly designed, installed and commissioned works well.
9. The simple calculators are simple because the math is simple
10. area m2 by U value W/m2t by design delta T (t) by heating hours = heat loss in kWh
11. Total kWh/run hours = kW *COP = size of unit you need ( this does not include DHW)
12. Need to add in for ventilation losses which will be small enough given the MVHR and a low ACH
13. In case you missed it
14. building new now just to the current building regs is a wasted opportunity. period.

sydthebeat

lkkev80 wrote: »

.......
Heating system I have in mind is ASHP with radiators but here is where we will need good advise...I prefer rads to reduce the cost of the heating system (am I correct that it is cheaper?) but obviously we need the right number of rads (thermal loading)....my fear with getting the wrong advise (ie somebody using a simple calculator that can be found on Internet for each room) is that they would say it is not possible to use the ashp with rads or else just plaster every free wall with big rads.......s

not necessarily cheaper than UFH, but probably will be.
Rads give off a different heat, and heat the room differently that UFH... they create a circular convection heatmovement where the higher you go the warmer the air. UFH heats the opposite, without convection, to create the warmest air lower down than higher up. People need heat lower down than higher up.... thus we have hair on our heads.

If you are using rad you ABSOLUTELY MUST have SR 50 calculations carried out on a room by room basis to size the particular radds you are going for (or are being provided to you). You should insist on seeing those SR 50 calculations before any work starts.