Underfloor throughout or mixed with Rads?

Hi, I’m about to start groundwork next week and have hit a brick wall in our decision on heating for bungalow (5 bed - 285 sq/m). We are getting a condensing oil boiler for cost reasons with possibility of switching to another heat source down the line. Just cant justify extra 15k for geothermal (or 10k for wood pellet) at the moment. We are putting our money into additional insulation/airtight membrane and MHRV to hopefully minimise the amount of heat required by the house. My architect recommends we go with a mixed system with underfloor in the living areas and rads in bedrooms. Our plumber however recommends underfloor throughout.

Arguments for mixed system are:
1) We are not heating bedrooms unnecessarily; give them a quick blast in the late evening and morning using timers.
2) Slightly reduced cost of not having to lay underfloor pipes in half the house (offset by cost of mixing valves to get mixed system to work correctly)
3) Architect reckons that the two systems work fine side by side as the return temperature from Rads is perfect for use in the underfloor and that possibly the plumber wants to install the simplest system rather than the best system.

Arguments for full underfloor system are:
1) Simplicity of system. Not complicating things by having 2 systems which work at different temps.
2) If we do switch to geothermal or similar down the line, the underfloor will work better with these.
3) Water doesn’t need to be heated to as a high a temperature leading to presumed lower amount of time the boiler needs to be working.
4) Efficiency of condenser is increased as there is a lower return temperature of the water, therefore the temp difference is greater between water and condenser part of boiler.

We need to decide on this in the next week or so as the floor maekup will be different depending on what we choose. I’ve read countless threads on here and other sites on the subject but cant decide. Have read a few threads which said that underfloor and oil are not a good combination at all and will cost a bomb to run but if we have better than average insulation and minimise drafts (no hole in the wall vents or open fires) would this still be the case? Maybe both systems will work ok? And it doesn’t matter what we pick.

Based on the arguments above, anyone have a tuppence worth to throw into the debate which might swing my mind in either direction?

In my humble opinion, from the research I have done in preparing for a self build stick with the one heat system in your house. Either go with rads all over or underfloor. Have you considered convection rads e.g. solo ? They work perfectly well with oil for now & also work very well with heat pumps if you chose to change at a later stage. People I spoke to said oil & underfloor was very expensive for them but as you stated above with a very high spec insulation in conjunction with the HRV it should be minimised.

I would say given that it is a Bungalow that you should go UFh all over, especially if you intend going over to geothermal at some stage..my tuppence worth...!!

Firstly, let me state that I have a vested interest in UFH, heat pumps HRV, Solar etc. If you want to embark on the heat pump route at a later date, then I would advise UFH. The trick is to run it at the lowest feasible temperature possible to get the maximum efficiency from the heat pump. If you implement it at 50 degrees, this does not bode well for heat pump efficiency. Normally we design UFH based on the heat source and the building fabric heat loss.

If you put underfloor throughout the house you can use any heat source you wish in the future and still get the maximum efficency from it. Convector radiators still operate around 45, so they are a compromise.
I would take issue with your architect. The two systems should be implemented in parallel as they operate at different temperatures.

With repsect it's also important to bear in mind that the concept of giving upstairs room a 'blast' does really make sense. The physics of heating a room to any temperature still requires the same heat energy. UFH if used with programmable stats (time and temperature) can be used to maintain a reduced temperature e.g. 16 degrees and can be programmed to raise the temperature at a certain time of day e.g. bedtime.

sman said:

Hi, I’m about to start groundwork next week and have hit a brick wall in our decision on heating for bungalow (5 bed - 285 sq/m). We are getting a condensing oil boiler for cost reasons with possibility of switching to another heat source down the line. Just cant justify extra 15k for geothermal (or 10k for wood pellet) at the moment. We are putting our money into additional insulation/airtight membrane and MHRV to hopefully minimise the amount of heat required by the house. My architect recommends we go with a mixed system with underfloor in the living areas and rads in bedrooms. Our plumber however recommends underfloor throughout.

Arguments for mixed system are:
1) We are not heating bedrooms unnecessarily; give them a quick blast in the late evening and morning using timers.
2) Slightly reduced cost of not having to lay underfloor pipes in half the house (offset by cost of mixing valves to get mixed system to work correctly)
3) Architect reckons that the two systems work fine side by side as the return temperature from Rads is perfect for use in the underfloor and that possibly the plumber wants to install the simplest system rather than the best system.

Arguments for full underfloor system are:
1) Simplicity of system. Not complicating things by having 2 systems which work at different temps.
2) If we do switch to geothermal or similar down the line, the underfloor will work better with these.
3) Water doesn’t need to be heated to as a high a temperature leading to presumed lower amount of time the boiler needs to be working.
4) Efficiency of condenser is increased as there is a lower return temperature of the water, therefore the temp difference is greater between water and condenser part of boiler.

We need to decide on this in the next week or so as the floor maekup will be different depending on what we choose. I’ve read countless threads on here and other sites on the subject but cant decide. Have read a few threads which said that underfloor and oil are not a good combination at all and will cost a bomb to run but if we have better than average insulation and minimise drafts (no hole in the wall vents or open fires) would this still be the case? Maybe both systems will work ok? And it doesn’t matter what we pick.

Based on the arguments above, anyone have a tuppence worth to throw into the debate which might swing my mind in either direction?

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hi,
i agree with startup