Advice needed on Ventilation / Heat Recovery systems

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benz1

51 posts

Master Geek

#204836 19-Oct-2016 12:58

Apologies in advance for asking about a subject that has been talked to death on this forum over the years but I'm really confused by all the options available for ventilation / heat recovery systems, .e.g., positive pressure, negative pressure, balanced, heat recovery, etc.

I have a 2 story home and my main objective is to keep it dry but also to add ventilation and add heat. I know the heating elements that come with these systems only take the chill off but is it possible to combine any of these systems with full central heating to heat the whole house?

I'd be grateful if anyone can point me in the right direction and recommend both the type of system I should be looking at as well as specific brands? SmartVent seems to have a good rep, are they a good option?

Thanks in advance.

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Uber Geek
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#1653527 19-Oct-2016 13:37

You can get combined ducted-heat-pump and heat-recovery-ventilation units. When I say heat recovery I mean an air to air heat exchanger that transfers heat from outgoing air to incoming air.

When we were looking at HVAC Smartvent did a heat pump HRV combination unit. In the end we went for separate heating and ventilation, but the smart vent air heat exchanger system was fantastic. The house was drier and felt a couple of degrees warmer. Our power bill decreased.

Mike

Kickinbac

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Ultimate Geek
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#1654803 19-Oct-2016 22:33

Check out mitsubishi electric. They can do a ducted heat pump linked with an HRV (lossnay) to pretreat the fresh air.

ronw

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#1654809 19-Oct-2016 22:42

If you are after a genuine heat recovery system try http://www.cleanaire.co.nz/

They offer a proper system with a heat exchanger in roof and fresh air pulled from outside feed through head exchanger where it is warmed by the stale air from inside home and then stale air is exhausted out to the outside.

I have not seen any other system in New Zealand that can compete with this system. You would have to find someone to install it I had a friendly electrician do it. The supplier can probably advise installers in your area. The Heat Exchanger has multiple inlets and outlets so its normal to have one inlet and outlet in each room. Small rooms like bathroom probably only need one.

if you need to discuss further pm me

Ps I have nothing to do with firm I only went with them because Consumer put me on to them and the product looked good compared with the alternatives

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mdf

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#1655522 21-Oct-2016 09:57

Are you looking for a gas fired or electric system? Pretty much are you already on reticulated gas or not.

benz1

51 posts

Master Geek

#1656373 22-Oct-2016 22:03

Thanks for the replies. From what I can tell, the three HRV's mentioned - SmartVent, Lassnay & Cleanaire, all perform a similar function. Does any one of them have advantages over the others?

@mdf, I am on mains gas.

Thanks again for the responses. This whole space is a minefield for the uninitiated like me!

mdf

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#1656692 23-Oct-2016 20:01

The economics of gas are that if you are already paying the (relatively high) fixed daily rate, it makes sense to get as many appliances on to gas as possible to maximise the (very low) per unit rate, particularly high energy users like heating. It would likely be very expensive going for an electric central heating option (ducted heatpump) and only using the reticulated gas for cooking and/or hot water. If you were really committed to a ducted heatpump (and there are some brilliant options), you should think carefully about getting the reticulated gas turned off.

In terms of systems to that do what you want, we are in a similar situation to you. We wanted central heating plus DVS/HRV air circulation. Like you, we thought that with all that ducting surely you could find something that would do both. We've just had a Bonaire gas ducted central heating system installed, because it advertises a fresh air ventilation add on. So far as I know, neither of the other primary options (Brivis and Braemar) have this option.

But I can only give it a mixed review so far. The system itself seems really good. Central heating works well, and the house is super quick to heat up when you turn it on. The fresh air ventilation seems to work - certainly there is a nice cooling effect on warm days that would otherwise be stuffy. It seems to be more of a DVS style positive pressure system than an HRV balanced one, even though there is return.

Where it's fallen over as far as we are concerned is in the smarts. You can program the central heating side of things on timer and thermostat, but the fresh air has to be controlled manually. In practice, this is proving to be a real pain. This limitation certainly isn't clear from the website. We're currently discussing this with Bonaire and the installer. There seems to be some hope that there is a solution, but it's not been deployed yet if there is.

So to be honest with you, if you wanted the full blown gas central heating combined with air circulation, there doesn't seem to be a solution ready right now. But if Bonaire does manage to sort out the controller issue, it should (touch wood) be a really good system. You might be better off waiting for a bit. Summer is coming anyway.

If you're in Wellington, I can strongly recommend the guys at Warmbreeze as installers.

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benz1

51 posts

Master Geek

#1656728 23-Oct-2016 22:22

@mdf, thanks, that's very helpful. The Bonaire system does seem to be a good solution for heating and as you say, it sounds like it can double up as a ventilation system, albeit a relatively simple one. I did note on their site in small print it says the ventilation can't be used at the same time as the heating which kind of makes sense. Can I ask what the solution is that you are hoping they come up with? I'd be grateful if you could let me know as and when they do provide a solution.

Yes, it would be more cost effective to use gas for ducted central heating. I do have a gas heater but tend not to use it very often as I also have a heat pump so really, I'm only using gas for water heating as I recently changed from a gas hob to an induction cooktop. I was wondering if it would be worth changin gover to electric water heating and get rid of the gas but if I were to go for gas central heating then it would make sense to keep it.

In hindsight, do you think it was a good idea to go for the integrated heating/ventilation system, or would it have been better to go for a separate, more advanced, ventilation system?

Thanks.

Kickinbac

468 posts

Ultimate Geek
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#1656732 23-Oct-2016 22:39

There are a couple of things that gas central central heating won't do... Cool and dehumidify.
The fresh air intake on the gas system can also be done on a ducted heat pump system. Its basically a motorised damper on a switch, on or off to take fresh air into the house. And its not a 'heat recovery system'.

Ragnor

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#1678096 26-Nov-2016 21:56

An HRV, Cleanaire or SmartVent only does does half the job and you generally still need heating or cooling depending on the outside air temperature.

If you can afford it go for the Mitsubishi or Fujistu systems that do aircon (aka ducted heatpump) and fresh air intake/ventilation.

Hammerer

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#1678134 27-Nov-2016 09:31

There are four functions mentioned here and you should evaluate your options based on all four:

heating
cooling
fresh-air ventilation
heat-recovery venitllation

I would not install fresh-air ventilation without heat recovery because most of the time I used it I would be pushing hot air (which I paid to heat) out of my house. I can open a window to get that.

Personally, I would not try to combine the ventilation and heating/cooling controls because the scenarios become more complex to an extent which simple control panels are not designed to handle.

Unless you have a heat-recovery system for your fresh air ventilation it shouldn't even be an option to combine heating/cooling with ventilation. The drivers for the functions are different: heating and cooling are generally set independent of outside conditions; ventilation is generally set relative to outside conditions, e.g. in winter we usually don't want fresh air brought in that is colder than the air inside. Likewise in summer we don't want hotter air brought in. Although a very efficient heat recovery system does nearly eliminate this dependecy, it does not eliminate it entirely.

Kickinbac

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Ultimate Geek
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#1678388 27-Nov-2016 16:21

In my opinion, ventilation can be incorporated with ducted air conditioning systems without using a heat recovery unit. For example, in the majority of commercial buildings ventilation/ outside air is introduced as 'minimum outside air', basically a calculation based on NZS4303 of 10 l/s per person. So say a ducted unit circulates 600 l/s, only 50 l/s is introduced as minimum fresh air, the rest is recirculated. In a domestic situation this could be done with a grille in a soffit with a balancing damper so outside is introduced while the system is running. A 230v motorised damper can also be incorporated with a switch so that the outside air can be switched on or off.
So you can run the system with or without outside air while heating or cooling. You can run the system on 'Fan only' to ventilate the house, probably when not home. The energy to heat or cool the minimum ambient outside air is probably minimal compared/offset by the significant additional cost of a heat recovery system (2-4 grand!).
In a brand new airtight house I would definately recommend a heat recovery unit.

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benz1

51 posts

Master Geek

#1678461 27-Nov-2016 18:59

Thanks for the replies but all getting a bit confusing. If I did want all four functions, i.e.,

heating
cooling
fresh-air ventilation
heat-recovery ventilation

then what are the most cost effective, recommended solutions?

Thanks.

Hammerer

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#1678487 27-Nov-2016 20:17

You would have to do the sums for your situation because your scenario will be different to mine. That makes a big difference as to what will be most cost effective. That's why there are so many discussions and so many of them are confusing because there are few guidelines that apply to everyone. Insulate first is the only one that I can think of.

In general, what Kickinbac says should work but we don't know the specifics of your situation. Kickinbac is saying that you would have to be able to recover the high capital cost of the heat exchanger by saving a lot. But neither of us know at what point a heat exchanger would give you a better return.

Here's some of the initial questions I would be asking because all these variables will be different than mine:

What temperature will will the whole house be heated to? And for which hours of the day or week? The higher your target temperature then the greater the benefit from doing something to save energy losses.
Will you also be cooling in summer?
Where do you live? So we can see the temperature profile and see the difference between indoor and outdoor temperatures.
What are your energy prices including night rates and the like?
Are you fully insulated: ceilings, external walls, floors? Insulation almost always gives the best economic return.
What are the house dimensions for floors, walls, ceilings, windows: areas and volumes; level of insulation; shape (rectangle, square, irregular)?
How long will you benefit from the system? If you are moving within a few years then most of the benefits go to the next owner.
Do you have a dust, damp, mould or condensation problem?

Kickinbac

468 posts

Ultimate Geek
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#1678530 27-Nov-2016 21:46

Where are you located? I suggest you contact a couple of local air conditioning companies and get some recomendations and quotes. Look for reputable brands such as Daikin, Mitsubishi Electric etc

benz1

51 posts

Master Geek

#1715882 5-Feb-2017 22:11

Kind of put this in the too hard basket as it was all getting very complicated and beyond my level of understanding. But I do need to put in some sort of ventilation system to dry out the house. If we forget about heating for the moment and focus on a standalone ventilation/heat recovery system, what should I be looking for? Is balanced generally recommended over positive pressure, etc? is the Cleanaire HRV a good option?

Thanks.

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