Marvin

An MVHR, in my opinion, should be within the thermal envelope to help keep the return temp the same as the temp inside the thermal envelope.

Hi @Andy T Good info from @JohnMo above. We went for a lower cold of -8 Centigrade which is about 4 degrees below the lowest temp recorded here in the the last 20 years. M

Hi Readers of the above post. This is a lovely idea but please be aware that the ideal site for Swift Nest Boxes is under the eaves or on walls facing north, northeast or north-west out of direct sunlight. Place five metres above the ground, with clear adjacent airspace so swifts can access it in a high-speed direct flight for best results.. Marvin

Hi @Tosh Who is the manufacturer, what is the type of MVHR?? Ah... It depends what type of unit your installing. Your layout shows 2 separate units?? Is the light blue thing the MVHR and the boxes manifolds? Or are the fan units in the blue and green boxes...???

Hi @Tosh I think that the red crosses are showing that the volume of air required at the indicated room outlet would have to travel too fast down the size of pipe suggested. This refers to the extract ducts.

HI @Coanda You are quite right, however the same 263m3 air flow unit will do both: the same push of air in, as the push of air out at the same time...... otherwise the building would blow up like a ballon... 😂 So this would be one 263m3 unit....

AS I understand it (having an MVHR for the last 6 years) In theory the MVHR unit pulls and pushes at the same time, your property being air tight.... , and therefore the flow rate refers to the flow of air through the building not the input or output.

Hi @Tosh It would really help if you showed us the layout. Usually you require 1 inlet any non wet room and one outlet on any wet room (wet rooms are loos showers kitchens, bathrooms, shower rooms and any room with a supply of water including utility rooms). However with larger or longer rooms you may need an inlet and outlet. I see nothing exceptional after looking at the design

Hmm.. Hi @Andehh Not sure if the figure you are changing allows for undershoot or overshoot or both.... Think this will depend on the ASHP model. I may be confused... If your floor takes along time to heat back up, personally I would keep the temperatures tight i.e. as soon as the floor slab loses temp reheat, otherwise it would take a long time to reheat?? It may also be the lack of a blending valve that's causing you challenges. Thinking how turning all those different zones on and off would effect the return temperature I wouldn't be surprised. Also how are you measuring the temperature in the bedrooms? Surely the air temp is what you want to know? If the heat from below was heating the air above surely the bedroom heating would only supplement the air temperature from below?? What happens when all the zones shut off?? Marvin.

Hi @JohnMo Yes my comment was if you were turning it off completely....

And what does your ASHP installation instructions say about turning on after leaving it off for hours when below 5 degrees Centigrade..... Mine says don't do it!

Hi @Andehh Thinking which is the right thing to do is excellent, and everybody has excellent suggestions, however as @ProDave is veering towards, it really depends on the maths, and then what controls you have which will allow you to change things when required to the optimum set-up. Remembering my plumbing days, the higher the ceiling the more heat used to achieve the temperature at the height of the temperature controls so your already at a disadvantage. I hope you have your roof insulated to within an inch of its life (we have a bungalow with ASHP PV, MVHR and good airtightness and insulation). Many, many, many, companies and people, ignore the important design and installation requirements required to achieve the most efficient use of an ASHP, mainly because each installation design requires individual consideration of the property its to be installed in. Without knowing much about your set-up. I would suggest trial and error. This is what we did. For us it turned out to be more efficient to have the Weather Compensation on and the ASHP on all the time, and adjust our wall thermostat between day temp and lower night temp. I assume you have underfloor heating below your carpet. We have radiators. So I would expect your temperature recovery would be much slower than ours. If you have a programmable thermostat I would try lowering the temp slightly before each cheap rate and increasing it during the cheap rate, but keeping it on all the time. Not sure why it freezes so badly. I'm sure that last comment will create a plethora of responses. Your comments suggest that the ASHP is struggling to produce the warmth required unless its on all the time topping up your home temperature. Recommended small works to check/improve: Insulate all pipework/ tanks/ controls (except of electrical elements/wires) outside the building thermal envelope to within an inch of its life. Insulate all primary circuit pipework excessively, insulate any other associated pipework. And, as @ReedRichards just commented the Weather Compensation needs to be related to your individual set-up/installation/home. It maybe fine it may not. I do not know. Good luck Marvin

Ditto. lovely steering wheel warmth....

I think that vehicles will need to be more thermally resistant... After all the aim is to keep the temperature inside the vehicle to a human desirable temperature.

Ok you win. Lighter weight per kWh of usable energy for those of you who miss understood my explanation.

Hi @SteamyTea Weren't you the one that said words to the effect of "don't turn the heating up wear an extra jumper."??? M

I think that is a long way down the line of development... Lighter weight per usable kW, and longer lasting, safe and far easier to recycle cheap batteries would be my first desire. When this is solved I would be a happy bunny. M

Yes we supplement the electricity purchased with our PV production to reduce the cost. Works very well between April and October.

I'm glad you wrote this!

Hi @Bornagain You are quite right! However our radiators are at 38 degrees C today and our home is fine. So radiators can be an option. However we DID insulate and air-tighten the property when we renovated (but this was to save on heating however the building was warmed - bottled gas boiler at the time).

When you read the report in full you will probably pick up on the fact that the government has been proactive over 50 years in implementing change. They taxed other ways of heating to discourage not using a heat pump. They trained people to install the systems properly. (to avoid bad publicity) They have well insulated properties. Pretty much everything we have not done.

See why the UK's heat pump market struggles while other countries succeed: https://www.theguardian.com/environment/2023/nov/23/norway-heat-pumps-cold-heating

Hmm.. Well I'm not a roofer but if you have holes letting wind through and damp air in the loft it could condensate in the area. However if it were me I would foam the holes until airtight from the loft and see what happens. Good luck M

Monitoring our MVHR results, with the inlet and outlet ducts and MVHR in our loft, we soon realised that the results were seriously effected by the loft temperature. We then super insulated the ducts and MVHR (2 to 300mm insulation to all) and we now have very good results in the high 80%. retained room temperature when using "heat recovery" (which also acts as cool recovery in the summer). Good luck M

We have 2 sheds. 1 with a waterproofed concrete floor and no condensation problems (no rusty metal things) in 5 years, and one on a block paving floor with condensation problems (rusty metal items) every year. The floor might be the cause..... Marvin