HRV- What to look for??

lollymob

Hi all,
I'm currently getting quotes for HRV for a new build (3000sq ft.) House will be well insulated, airtight, underfloor heating throughout with geothermal heat pump. There is quite a difference between quotes I've been getting so far. Has anyone any ideas what I should be looking for- Size of unit/ducting/air changes per hour/efficiencies? Any advice would be very appreciated as I am way out of my depth here!!
Many thanks,
lollymob

runawaybishop

lollymob wrote: »

Hi all,
I'm currently getting quotes for HRV for a new build (3000sq ft.) House will be well insulated, airtight, underfloor heating throughout with geothermal heat pump. There is quite a difference between quotes I've been getting so far. Has anyone any ideas what I should be looking for- Size of unit/ducting/air changes per hour/efficiencies? Any advice would be very appreciated as I am way out of my depth here!!
Many thanks,
lollymob

Got one in a few years ago, hilarious differences between the quotes for similar systems. Was quoted often for units underpowered for my requirements.

You need to calculate how powerful the HRV unit needs to be to supply you with 1/3rd of an air change an hour running on minimum. If they arent running on minimum the majority of the time you drastically decrease their efficiency.

For a 279 m^2 house with 2.4 m ceiling heights you are talking about shifting 1/3rd of this 670 m^3 (i.e 1 full change every 3 hours, which i believe is the recommended amount) - so 223 meters^3 an hour. The unit you get quoted for needs to be able to shift that on minimum.

You will need to site the unit somewhere suitable. Not too far away from an external wall be over an area that is not used much as they do make noise.

Check if your quote includes not just installation but insulation of all ducting and what type of ducting will be used. Rigid ducting is cheaper but conducts sound more than flexible so baffles should be used. These units aren't that hard to install, consider doing it yourself or gettign a competent tradesman to do it for you. I put my own in with my sparks.

lollymob

runawaybishop wrote: »

Got one in a few years ago, hilarious differences between the quotes for similar systems. Was quoted often for units underpowered for my requirements.

You need to calculate how powerful the HRV unit needs to be to supply you with 1/3rd of an air change an hour running on minimum. If they arent running on minimum the majority of the time you drastically decrease their efficiency.

For a 279 m^2 house with 2.4 m ceiling heights you are talking about shifting 1/3rd of this 670 m^3 (i.e 1 full change every 3 hours, which i believe is the recommended amount) - so 223 meters^3 an hour. The unit you get quoted for needs to be able to shift that on minimum.

You will need to site the unit somewhere suitable. Not too far away from an external wall be over an area that is not used much as they do make noise.

Check if your quote includes not just installation but insulation of all ducting and what type of ducting will be used. Rigid ducting is cheaper but conducts sound more than flexible so baffles should be used. These units aren't that hard to install, consider doing it yourself or gettign a competent tradesman to do it for you. I put my own in with my sparks.

Many thanks for your reply. The differences in some quotes are unbelievable!! Some companies are recommending two units for size of our house others have said no need smaller unit would do fine!! Most are advising rigid ducting only. It's very difficult to compare quotes when I don't know what to be looking for and of course all salesmen believe their system is the best!! I will definitely check about the insulation.
Thanks again for your advice!
Lollymob

beyondpassive

Make sure to get one with summer Bypass and Boost function. The system should be designed, with pressure drops designed to handle 0.4 air changes nominal, efficient fans and heat exchanger independently tested. They should be able to supply a commissioning cert with supply and extract rates in balance, cert should also show how it complies with background part F ventilation table 1 rates and boost rates table 2. Silencers and cross talk attenuators where required.

runawaybishop

lollymob wrote: »

Many thanks for your reply. The differences in some quotes are unbelievable!! Some companies are recommending two units for size of our house others have said no need smaller unit would do fine!! Most are advising rigid ducting only. It's very difficult to compare quotes when I don't know what to be looking for and of course all salesmen believe their system is the best!! I will definitely check about the insulation.
Thanks again for your advice!
Lollymob

They will all recommend the unit they carry. Find out how many air changes an hour that unit can handle and what speed it will be running at. Rigid ducting is louder than flexible, make sure they are including sound baffles - this is important

As beyondpassive mentions you can then look for stuff like multiple remotes, boost functions, automatic co2 detection, moisture detection, summer bypass etc. Keep an eye out for units that can heat the air coming in in bad frost as it can be a lot quieter than other units that just circulate air on full for a bit.

For what its worth I think I spent about 2.5k-3k on my unit 3 years ago.

lollymob

Thanks a million for all the advice, I will keep all of this in mind as I go through all the quotes.

sinnerboy

Look for

a co-link to your fire alarm system - you don't want the vent fan motor running when there is a fire

fire resistant ceiling outlets/inlets.

Rigid ducting is less prone to collapse and consequent inefficient or even innefective ventilation.

runawaybishop

sinnerboy wrote: »

Look for

a co-link to your fire alarm system - you don't want the vent fan motor running when there is a fire

fire resistant ceiling outlets/inlets.

Rigid ducting is less prone to collapse and consequent inefficient or even innefective ventilation.

You can get ceiling inlets that shut off in the event of fire, they are a fair bit less expensive than hooking the system into your fire alarm. Agree that rigid ducting can be better (more efficient air transfer also), just pointing out the noise issue.

sinnerboy

The sinner to the bishop

I would not compromise on fire safety myself.

https://www.youtube.com/watch?v=jQV_MJwYQ3k

https://www.youtube.com/watch?v=1-d0-WHqyrE