Quantifying the benefits of low temperature UFH systems.
A friend of mine works for a company designing and selling UFH systems and he is always asking me for figures on the actual difference made by changing the pipe spacing from 200-300mm to 100mm centres. For a long time a lot of people in this industry have known that it makes sense to use as much pipe as possible, especially with Heat Pump systems, so as to be able to operate at lower flow temperatures. The government recently released a document titled RHI FAQs which contains some worked examples for RHI payments and estimated savings for two typical houses with energy requirements of 10,000 and 18,000kWh/year. This gives me the perfect opportunity to get down to the nitty gritty and put some actual figures together to highlight the benefits of low temp UFH systems. Working the numbers back using our version of the MCS heat loss calculator suggested that they got to these figures using a flow temperature of 50DegC.
For the larger house (i.e. approximately 210m2) RHI payments and nominal running cost savings are around £2,520/y (GSHP) and £875/y (ASHP).
For the smaller house (i.e. approximately 120m2) the combined RHI payments and savings are around £1,400/y (Ground Source Heat Pump) and £485/y (Air Source Heat Pump).
So I decided to run these calculations again but with a flow temperature of 35DegC which you can see from the MCS Heat Emitter Guide does correspond closely with reducing the pipe spacing from 300mm to 100mm for houses with mid-range heat loss. As expected there is a significant difference in RHI payments and operational costs which I have shown below.
For the larger house (18,000kWh/y, app 210m2) the increased benefit of RHI and operational cost savings is £2,865 (GSHP) and £1,200 (ASHP) which equates to an increase of around £335/year or around £2,345 over the 7 year period.
For the smaller house (10,000kWh/y, app 120m2) the increased benefit of RHI and operational cost savings is £670/y (ASHP) and £1,590/y (GSHP) which equates to an increase of around £190/year or around £1,300 over the 7 year period.
Obviously these figures become more pronounced with larger houses or properties with larger annual heat demands so for a larger house (i.e. 375m2) with a demand of around 28,000kWh/y the difference in benefits going from 50DegC to 35DegC is more like £540/y or just under £3,800 over the 7 year period.
Hopefully the above figures will show people that it is cost effective to purchase a low temperature heating system as there will be a significant increase in RHI payments and reductions in operational costs to balance the increased capital costs. Also, at the end of the 7 year RHI period you will still have the benefit of a low temperature heating system that will continue to provide operational cost reductions throughout its lifetime. In other words – if you are aiming at efficiency then low temperature UFH systems are the way forward. Energy efficiency is an investment but it is one that is well worth while.