HRV System

[Dell]

I just bought a house that has an HRV system. I've done a search here and read some older posts, some happy and others not happy about their HRV. Would you mind sharing information and tips on your system? Do you have it on year round? If so, what setting do you keep it on in the summer - and what setting in the winter?

[Nienke]

We installed a DVS system a couple of years ago, probably the same principle as the HRV, and it made a big difference. No more weeping windows! I have it on year round, but we have summer-autumn-winter- spring settings. I also have an outside vent which is used in the summer setting, it brings in fresh air from outside in stead of the roof (too hot in summer).
Settings are automatic in my system but I can adjust when need be. On a very wet day I crank up the settings a little bit otherwise I leave the system run by itself.

[Super_BQ]

I would be interested on the operating cost of the HRV / DVS system? When in operation, how many watts does it consume to drive the fans? If I recall correctly, the newer HRV systems also draw outside air from the suffit instead of in the roof space? However, HRV still relys on a positive ventilation method where air is blown to rooms and not fed back through a central registry intake ducting (closed system).

[Nienke]

I haven't noticed any difference on my electricity bill to be honest, it uses so little. 'My' dvs system draws air from the roof space when it's not on summer setting, and draws air from outside in summer setting. It varies the fan speed according to the temperature in the roof space, and it can even alternate between outside/roof vent dependent again on roof temperature (autumn/spring setting). In winter is will increase speed when temperature is up and reduce speed when temperature is low. DVS is not a closed system.

[72andsunny]

I would be interested on the operating cost of the HRV / DVS system? When in operation, how many watts does it consume to drive the fans? If I recall correctly, the newer HRV systems also draw outside air from the suffit instead of in the roof space? However, HRV still relys on a positive ventilation method where air is blown to rooms and not fed back through a central registry intake ducting (closed system).

IIRC a standard HRV fan uses 8 watts. The quote for our somewhat large 3 bedroom house required an install with 3 fans for a total of 24 watts. I believe the stairwell was going to have something much stronger to "keep the hot air downstairs"...I assume that fan would have used more than 8 watts.

[Super_BQ]

I still question the effectiveness of HRV/DVS in NZ climate. I recall reading a study in Dunedin about the use of DVS. Their conclusion was in the S. Island, roof temperatures do not get hot enough in winter to make it any benefit to the living space. Discussions below:

http://www.stuff.co.nz/life-style/50...eating-roasted
http://www.communityenergy.org.nz/ho...dback-welcome/

On another point, the article below talks about the problems of recessed ceiling lights with roof atic space. (though lightning isn't the topic of discussion, the issue of attic space temperature is)

http://m.theglobeandmail.com/life/ho...service=mobile

Home builder sensationalist Mike Holmes explains that the roof of a house is a cold zone and it's temperature SHOULD be close to what the outside air temperature is. So in winter months if you're in the S. Island, indoor temperature requirement is always higher than the outside air temperature.

Beneficial aspect of HRV/DVS may be to control the extremes of condensation forming. But in the terms of regulating temperatures? - i'm not so sure.

[Nienke]

It's not for regulating temperatures (although HRV claims that but it's simply not true), but it's for regulating condensation and to dry out the house. Even though it's blowing in 'colder' air (I'm on the North Island) in winter, the air is dry coming from the roof and therefore easier to heat.
The HRV sales person that came to my house even claimed I would never ever have to vacuum again..... sjeez. Suffice it to say that I went with DVS who had a more honest story about what their system can and cannot do. And they were right, the moment DVS was switched on my windows were dry and I've had no more weeping windows even on cold and wet winter days with the dryer going and cooking at the same time. I sound like a sales person, but I'm not

[sophiedb]

I don't know about temperature or energy use, but I do know that since we installed the DVS I don't need to get up early on a winter's morning to mop the windows. That's plenty enough for me.

[Dell]

Thanks for everyone's input!

[Dell]

In Opua, it has been raining on and off since yesterday. This morning the humidity level in the house was 81%. I turned on the HRV system, left the windows open a few inches and the humidity dropped to 77% within an hour or two. Then I closed the windows (leaving the HRV on) and the humidity is down to 72%!