New build: solar panels and underfloor heating

minnow

Hi,

I'm buying a new build which is at an advanced stage of construction, 2800 sqft. House rated as BER A2 with underfloor heating and air-to-water heating. I am now considering adding solar tubes for hot water as a means to reduce electrical bill over coming years, need to understand does it make sense.

Would the hot water from the solar system only heat the hot water system or also contribute to the UFH? In such a well-insulated house, do you think that adding such a system would pay for itself, or will the reduction in the costs of running the heat pump be minimal?

[font=Open Sans, Arial, sans-serif]Any thoughts would be appreciated.[/font]

KCross

Solar is a waste of your money when you have a HP.
Do the math on it. What does the Solar cost to install? €5k? Lets say you save €200/yr(wildly over estimating there) on electricity for hot water... it will take 25yrs to pay for itself.

You will run the HP for a long time before you burn €5k of electricity and that would be to just break even plus you now have a whole new system to maintain so there will be maintenance costs.

Calahonda52

As KC: better spent on upgrading the planned insulation
OP whats the projected airtightness number?
Does it have MVHR?

ferryman35

It goes against conventional practice here.....but it's not as mad an idea as it first sounds! At least one leading manufacturer design their heat pump systems around the concept of incorporating energy from other sources.

All solar has a long payback but you benefit most if you can incorporate the solar energy you harvest into your heating as well as your hot water system. Now most will say that when the solar yield is best you won't want heat at all....but in our climate there have been plenty of times when we have had bright sunny days and evenings where you'd be glad to run the heat for a while.

You need a good system and a good installation to get the benefits, but so long as you can stump up the initial investment, it will give you a return, done right.

minnow

Calahonda52 wrote: »

As KC: better spent on upgrading the planned insulation
OP whats the projected airtightness number?
Does it have MVHR?

The house has whole house mechanical ventilation, with heat recovery. I don't have the air tightness number, but as an A2 house, I presume it will be pretty good.

BryanF

minnow wrote: »

The house has whole house mechanical ventilation, with heat recovery. I don't have the air tightness number, but as an A2 house, I presume it will be pretty good.

ask what has been specified in the contract spec

quentingargan

You may have no choice but to add solar. In an A2 house, the renewables contribution from your heat pump may not be enough because you don't use the heat pump enough.

To my mind, solar PV has fallen in price so much that it is more cost effective than solar hot water. If you have MHRV, you will use some of the power from the PVs running this and daytime loads, and you can use a device to divert your surplus electricity to the hot water immersion heater.

The main advantage over thermal is that there is no anti-freeze to change every two years, and no moving parts.

Has your BER assessor advised if you need a renewable energy component to comply with Part L?