MVHR - Short on time, what option is best?

[boxrick]

I am completely gutting my house, hopefully getting it quite airtight and installing a warm side ceiling void

I have been quoted basically 7.5k + VAT ( design/ supply and commission without install ) and 8.5k+ VAT ( design and supply. No commission or install ) by 21 degrees and Paul Heat Recovery respectively, regarding MHVR install of a Zehnder Q350 + pipes + silencers and cooling battery.

My first fix is looking to be around early July, and my final fix around late August. 

Simply put I am being quoted around 4-6 weeks for the design, when I am guessing I will need all my stuff much sooner than that.

So my question is... whats my best option at this point? Do I just pay the deposit to one of these companies and hope for the best? Is a self guided route going to give me the same sort of performance and acoustics one of these companies is likely to specialise in?
 

Any guidance or direction would be appreciated!

 

 

[JohnMo]

17 minutes ago, boxrick said:

cooling battery.

Don't waste you money - read the many threads on here.

 

At those prices I would be doing it myself and did. Your layout lends itself to a nice simple cascade system.

 

First MVHR move away from bedrooms and install in cycle store.

 

I would flow into dining and into office from there only. Dining flow will be most the house volume flow out of two outlets.

 

Extract from all wet rooms and plant room. All other areas will be ventilated via cross flow or transfer flow.

[boxrick]

Don't bother with the cooling battery? Is it not worth it to temper the temperature (probably downwards) a few degrees?

 

 

 

 

 

[JohnMo]

2 minutes ago, boxrick said:

Don't bother with the cooling battery? Is it not worth it to temper the temperature (probably downwards) a few degrees?

 

Let's consider a few factors

 

Air change rate. MVHR is in the range of 0.3 to 0.5 air changes per hour. Impact on room temp is almost zero. Two windows open on different sides of the house could 6 to 8 ACH.

 

Look at the performance chart of cooling batteries, apply your flow rate and the cooling water flow temp and see the resulting kW heat removed. It is small.

 

If you have cooling water, spend money on a fan coil or two instead of radiators or as well as UFH. If you have UFH just push the water through the floor, it's free cooling with solar PV.

 

[boxrick]

I see, in my case I was going for a highly insulated / airtight build. I was worried about the cooling within the house, initially I was looking those dual Daikin heating / cooling heatpump systems but not can be funded under the BUS programme. 

So my thoughts were in the hottest days of summer or perhaps in the middle of the night, being able to drop the general air temp a few degrees would be a whole lot better than no control? I appreciate it isn't really a 'cooling' unit but more an air tempering unit. 

I am having 9 triple glazed Fakro rooflights with the electrical external covers and electrical which I should be able to open to hopefully get a big heat reduction if it does get too warm.

Edited June 3 by boxrick

[JohnMo]

Just now, boxrick said:

dual Daikin

You only need a single ASHP that does both. There is NO restrictions on cooling within BUS funding. There is via permitted development, but that is different.

 

Just get a heat pump that does heat and cool out the box, Panasonic, Hitachi etc

 

2 minutes ago, boxrick said:

perhaps in the middle of the night

Open windows?

[-rick-]

22 minutes ago, JohnMo said:

You only need a single ASHP that does both. There is NO restrictions on cooling within BUS funding. There is via permitted development, but that is different.

 

I think the recent changes to PD has removed this:

 

https://mcscertified.com/new-permitted-development-rules-in-england-air-source-heat-pump-installations-must-now-comply-with-mcs-020-a/#:~:text=On Thursday 29 May 2025%2C the UK government,pump from 0.6m3 to 1.5m3 for dwelling houses.

[JohnMo]

Point is why two heat pumps? When one will switch between the heating and cooling. Hitachi even have an auto settings that will automatically switch between the two settings based on what a intelligent thermostat reads.

[Oz07]

Regarding design have you enquired with bpc? I don't remember having to wait that long for a plan. More like a week or 2. You don't have to buy the kit from there just pay for design. 

[Mike]

5 hours ago, boxrick said:

So my thoughts were in the hottest days of summer or perhaps in the middle of the night, being able to drop the general air temp a few degrees would be a whole lot better than no control? I appreciate it isn't really a 'cooling' unit but more an air tempering unit. 

Yes, would make a small difference and I've installed one myself (though it's unlikely to be operational this summer). However I've only done that because it was the only practical method - no chance to chill the UFCH or add aircon in my case; if I could have done either, I would have.

 

6 hours ago, JohnMo said:

First MVHR move away from bedrooms and install in cycle store.

+1. Mount it on the ceiling if necessary (using a suitable unit).

[Nick Laslett]

Sorry to be less than useful, I have the Comfopost cooling/heating add on with my Zehnder MVHR. As recommended by Pauls. 
 

But my system is not yet commissioned, so no idea if it adds much. 
 

There has been much discussion on this topic here at Buildhub, with general consensus that it isn’t worth the money fitting the comfopost. Search on my name should surface these earlier discussions. 

I am only looking to reduce the temperature of the upstairs rooms in the house by 3°C. 
 

I have multiple cooling strategies for my house, but was not aware of the fan coil radiators until too far into my build. 
 

 

 

[boxrick]

6 hours ago, Mike said:

Yes, would make a small difference and I've installed one myself (though it's unlikely to be operational this summer). However I've only done that because it was the only practical method - no chance to chill the UFCH or add aircon in my case; if I could have done either, I would have.

 

+1. Mount it on the ceiling if necessary (using a suitable unit).

My plant room is located right next to shaded trees, surely it would be the best place for it? If my walls are insulated enough I shouldn't really hear it? 

[JohnMo]

18 minutes ago, boxrick said:

My plant room is located right next to shaded trees, surely it would be the best place for it? If my walls are insulated enough I shouldn't really hear it? 

What difference does the shaded tree make to plant room location?

 

As I mentioned previously you can make install super simple, and reduce the number of ducts required etc. by moving the MVHR

 

You can make the original location work, but you need to detail how the walks are built. If stud walls, you need 2x layers of 18mm ply on the full wall to dampen any vibration and high density insulation.

 

Heat pump or boiler? Where are they located?

[boxrick]

11 minutes ago, JohnMo said:

What difference does the shaded tree make to plant room location?

 

As I mentioned previously you can make install super simple, and reduce the number of ducts required etc. by moving the MVHR

 

You can make the original location work, but you need to detail how the walks are built. If stud walls, you need 2x layers of 18mm ply on the full wall to dampen any vibration and high density insulation.

 

Heat pump or boiler? Where are they located?

Heatpump ( getting a heatgeek to design and install UFH / ASHP system for me ) , see blue for likely or red for preferred but unlikely ( depending on land swap with neighbour )

 

[Nickfromwales]

15 hours ago, boxrick said:

I am completely gutting my house, hopefully getting it quite airtight and installing a warm side ceiling void

Apologies for my confusion, but is this a warm or a cold attic (roof)?

[boxrick]

23 minutes ago, Nickfromwales said:

Apologies for my confusion, but is this a warm or a cold attic (roof)?

Yea... as seen in other thread. Warm roof. 

[Nickfromwales]

2 minutes ago, boxrick said:

Yea... as seen in other thread. Warm roof. 

Then you have plenty of options to route MVHR ducts, but the 2 companies you mention typically favour series run systems with galv distribution ducting, whereas I always use a radial setup with 92 or 75mm ducts; the aforementioned companies often specify systems which also require cross-talk and acoustic inline attenuators, which are a complete PITA to integrate into the fabric of a build. Would not be my first choice tbh, sorry.

[boxrick]

So actually, from the sounds of it. Sacking off the companies, designing my own system based on feedback here is probably a better option?

[Mike]

35 minutes ago, boxrick said:

So actually, from the sounds of it. Sacking off the companies, designing my own system based on feedback here is probably a better option?

Yes, it probably is :)

[tuftythesquirrel]

Agree with  @Nickfromwales and decided on a 75mm radial setup. I have a friend that has installed other (series) types, as a living, but said they are a PITA, when you find that the friggin big attenuator on the design, won't fit between the joists etc. I think you would have less acoustic issues with this type of install. I got my kit from Blauberg and designed and fitted it myself. At the time (about 2 years ago) some companies would give you a basic design but things seemed to have tightened up a bit since then. None of the companies wanted to supply/extract from hallways, cloakrooms and plant room etc. so I added this as I thought it was worthwhile. In the end I couldn't see the value of paying for their design, if they weren't going to follow my requirements.

 

I read the Blauberg manual did more research and came up with a set of design rules:

 

• Place intake on north side of building.
• Keep AHU away from bedrooms.
• Do not place valves above showers (Outside shower area)
• Place the Kitchen Extract Valve near the sink, not above the cooker.
• Kitchen, Bathroom, En-Suite and Utility Valves require a double duct run.
• If the duct run is greater than 15m, double the ducting.
• If the duct run is greater than 20m, triple the ducting.
• If the room is greater than 20m2, the valve requires a double duct run.
• Do not exceed runs of 30m.
• Keep the AHU flow rate as low as practicable.

I did a spreadsheet with the building regulations ventilation supply and extract rates plus the additional rooms I wanted and worked back to make sure the total wasn't more than 50-60% of the AHU's capacity. The general consensus on the forum seemed to be is that you can run at a lot less than BR supply rates in practice.

 

@Jeremy Harris  has kindly put a commissioning procedure on the forum (what a guy!).

 

 

[JohnMo]

16 minutes ago, tuftythesquirrel said:

• Place intake on north side of building. 
• Keep AHU away from bedrooms.
• Do not place valves above showers (Outside shower area)
• Place the Kitchen Extract Valve near the sink, not above the cooker.
• Kitchen, Bathroom, En-Suite and Utility Valves require a double duct run.
• If the duct run is greater than 15m, double the ducting.
• If the duct run is greater than 20m, triple the ducting.
• If the room is greater than 20m2, the valve requires a double duct run.
• Do not exceed runs of 30m.
• Keep the AHU flow rate as low as practicable

Some comments on the above

 

Intake placement makes little difference as long as BOTH inlet and outlet on the same face of building. This is for pressure balance.

 

Keep away from bedrooms is wise, but with careful design can be placed there.

 

Extract over shower areas, many schools of thoughts on that subject, really makes little difference as long as the extract isn't next to door, so room gets washed with fresh air.

 

Kitchen extract, not above hob is good advise. But place for longest distance from likely supply terminal to wash whole kitchen with fresh air.

 

Kitchen etc need double runs - no, flow rate, length, diameter and overall pressure drop, make the case for number of runs. Nothing else.

 

Rooms greater than 20m² need double runs, see above

 

Keep ACU flow as low as practical. Not really, you need to keep pressure drop at either side of ACU (or MVHR) as low as possible. This means fan runs lower on its performance curve (so rpm for a given flow rate) and therefore less noise is generated for a given flow rate.

 

[Tony L]

@boxrick, I think your blue ASHP is too close to the window; it should be 1m min. away.

[boxrick]

16 hours ago, Tony L said:

@boxrick, I think your blue ASHP is too close to the window; it should be 1m min. away.

I'll move it closer to the border. Sadly looks like it's going to be the blue one now

[JohnMo]

17 hours ago, Tony L said:

@boxrick, I think your blue ASHP is too close to the window; it should be 1m min. away.

 

4 minutes ago, boxrick said:

move it closer to the border. Sadly looks like it's going to be the blue one now

The 1m rule only really applies to R290 heat pumps. R32 doesn't make much difference. 

[FarmerN]

On 03/06/2025 at 08:22, JohnMo said:

 

First MVHR move away from bedrooms and install in cycle store.

 

I would flow into dining and into office from there only. Dining flow will be most the house volume flow out of two outlets.

 

Extract from all wet rooms and plant room. All other areas will be ventilated via cross flow or transfer flow.

Are you suggesting no inlet ducts to the bedrooms or have I misunderstood?