R
ralsmith1
For the last 3 days I have been extensively researching how to heat my new build bungalow in the most energy efficient way. It is a super insulated shell at the moment - at near passive house levels. It's only 50sqm - all open plan (except bathroom) with 'Optitherm' double glazed windows and skylights. Heat Recovery Ventilation is going to be used. Tiles and UFH throughout. (Radiators not an option as VERY high ceiling heights in some areas.)
Unfortunately, I'm not going to be able to use lots of solar water heaters as my planning consent won't allow it. Great shame!
So here goes a brief description of my research findings on this.
My original idea was to go with an Air Source Heat Pump and a small solar water heater and to use wet UFH. This would mean I could do away with a gas boiler and just have an immersion in my cylinder for back-up.
However, having researched heat pumps in detail it seems that they have one serious problem (apart from the CoP going down in Winter). Apparently they are VERY prone to icing up in the UK's damp climate - and not just at sub-zero temps. The exhaust air from the pump is very cold and moisture in it will freeze. The machine will then have to go through an energy sapping de-frost cycle to perform again. I have been told that this can happen as frequently as every half hour in bad conditions making their efficiency worse than even elec immersion heaters.
T overcome this I looked into blowing exhaust air from the HRV over the Heap pump but decided this wouldn't make much difference to the icing problem.
The nail in the coffin for this option was that the heat pumps need servicing and the condensers need replacing before the 'pay-back' is complete.
So I decided to look into the new 'ribbon' type electrical UFH. I will not need to heat the property frequently (if the insulation does its job properly) and I thought this may be the way forward.
The heat-up times are amazing for this product and with the type of house I am building, this is very important - I need to heat quickly and efficiently and let the insulation and HRV do the rest. (Wet systems simply don't have this very important quality - what with having to heat up the whole screed before you start on the actual room.)
I have found many mixed opinions on forums about these systems and the people I have talked to have given me mixed feedback as well. I am actually fairly convinced they would provide me with an inexpensive heating method. However, I have not been able to find ANY tech data supporting this.
For this reason and the fact that elec heating is widely know to be expensive, I have thrown this option into the 'not so green' recycling bin.
So, wet UFH was the only option but with the standard warm-up times they have, this wouldn't work either.
HOWEVER... I have found a retrofit product that can be laid ON TOP of a screed. It uses 18mm boards that a 12mm pipe is pushed into and you can tile directly over the top of it using flexi tile adhesive. The whole kit including manifolds and thermostats will cost me less than £2k. (I'm new to the forum and don't think we're allowed to mention brands so I won't.)
I am going to put about 30mm of crush resistant insulation directly underneath it to avoid heating up my screed and I am very confident that it will achieve warm-up times as fast as elec UFH.
I am now fairly sure (definitely not 100% though) that the way forward for me is to have a modern condensing gas boiler running the wet UFH system described above and heating my hot water. for the following reasons...
1. We know that wet UFH is cheaper that elec. Ribbons might come close to it but def won't beat it.
2. Having wet UFH keeps my options open for the future. I can easily fit electrically operated heat pumps (if gas becomes prohibitively expensive), solar water heaters if the planners ever relax (!) or any future water heating invention (if I invent a time machine). With elec UFH I onl have one option for the future - electricity.
3. I'd be putting in a boiler anyway to heat my hot water.
On a final note, one pet hate of mine with wet UFH is that the boiler is constantly switching itsef on and off. My solution for this is to get the bioler to heat water in a cylinder. The UFH then heats its water by passing through a coil in this cylinder. This is doubly sensible as it will mean retrofitting solar or heat pumps is easier.
Please send through comments if you think my research has led me down a garden path rather than a yellow brick road!!!
Unfortunately, I'm not going to be able to use lots of solar water heaters as my planning consent won't allow it. Great shame!
So here goes a brief description of my research findings on this.
My original idea was to go with an Air Source Heat Pump and a small solar water heater and to use wet UFH. This would mean I could do away with a gas boiler and just have an immersion in my cylinder for back-up.
However, having researched heat pumps in detail it seems that they have one serious problem (apart from the CoP going down in Winter). Apparently they are VERY prone to icing up in the UK's damp climate - and not just at sub-zero temps. The exhaust air from the pump is very cold and moisture in it will freeze. The machine will then have to go through an energy sapping de-frost cycle to perform again. I have been told that this can happen as frequently as every half hour in bad conditions making their efficiency worse than even elec immersion heaters.
T overcome this I looked into blowing exhaust air from the HRV over the Heap pump but decided this wouldn't make much difference to the icing problem.
The nail in the coffin for this option was that the heat pumps need servicing and the condensers need replacing before the 'pay-back' is complete.
So I decided to look into the new 'ribbon' type electrical UFH. I will not need to heat the property frequently (if the insulation does its job properly) and I thought this may be the way forward.
The heat-up times are amazing for this product and with the type of house I am building, this is very important - I need to heat quickly and efficiently and let the insulation and HRV do the rest. (Wet systems simply don't have this very important quality - what with having to heat up the whole screed before you start on the actual room.)
I have found many mixed opinions on forums about these systems and the people I have talked to have given me mixed feedback as well. I am actually fairly convinced they would provide me with an inexpensive heating method. However, I have not been able to find ANY tech data supporting this.
For this reason and the fact that elec heating is widely know to be expensive, I have thrown this option into the 'not so green' recycling bin.
So, wet UFH was the only option but with the standard warm-up times they have, this wouldn't work either.
HOWEVER... I have found a retrofit product that can be laid ON TOP of a screed. It uses 18mm boards that a 12mm pipe is pushed into and you can tile directly over the top of it using flexi tile adhesive. The whole kit including manifolds and thermostats will cost me less than £2k. (I'm new to the forum and don't think we're allowed to mention brands so I won't.)
I am going to put about 30mm of crush resistant insulation directly underneath it to avoid heating up my screed and I am very confident that it will achieve warm-up times as fast as elec UFH.
I am now fairly sure (definitely not 100% though) that the way forward for me is to have a modern condensing gas boiler running the wet UFH system described above and heating my hot water. for the following reasons...
1. We know that wet UFH is cheaper that elec. Ribbons might come close to it but def won't beat it.
2. Having wet UFH keeps my options open for the future. I can easily fit electrically operated heat pumps (if gas becomes prohibitively expensive), solar water heaters if the planners ever relax (!) or any future water heating invention (if I invent a time machine). With elec UFH I onl have one option for the future - electricity.
3. I'd be putting in a boiler anyway to heat my hot water.
On a final note, one pet hate of mine with wet UFH is that the boiler is constantly switching itsef on and off. My solution for this is to get the bioler to heat water in a cylinder. The UFH then heats its water by passing through a coil in this cylinder. This is doubly sensible as it will mean retrofitting solar or heat pumps is easier.
Please send through comments if you think my research has led me down a garden path rather than a yellow brick road!!!
