Balanced ventilation with heat recovery

Forums › Home Workshop DIY › Balanced ventilation with heat recovery

1 | 2 | 3 | 4

20581 posts

Uber Geek

Trusted

Lifetime subscriber

#2709391 19-May-2021 07:19

Kickinbac makes a very good point about ducted systems. They sit outside your insulated envelope, pushing air through ducts that are usually R0.6 (they have about 1cm of insulation) and they make a hole in your insulation. Before we put the ducted system in we couldn't hear rain inside our house at all, now we can hear it very clearly through the diffusers in each room and through the large return vent. The house cools down more quickly when the system isn't on as well.

Highwall units are louder and uglier, but they sit inside the thermal envelope. Multi-split systems use one outdoor unit and multiple indoor units, which is tidier but may be less efficient. I wouldn't really want five outdoor units, ugly and more maintenance required.

SumnerBoy

2074 posts

Uber Geek

ID Verified

Lifetime subscriber

#2709401 19-May-2021 08:06

Our ducted system would live inside the thermal envelope. With only two small holes for the pipes to run to the outdoor unit.

I think for our case a single ducted system with some basic zone control might be sufficient and the most cost effective.

timmmay

20581 posts

Uber Geek

Trusted

Lifetime subscriber

#2709450 19-May-2021 08:20

SumnerBoy: Our ducted system would live inside the thermal envelope. With only two small holes for the pipes to run to the outdoor unit.

I think for our case a single ducted system with some basic zone control might be sufficient and the most cost effective.

How would you manage that? The ducted indoor units are pretty large and fairly loud.

SumnerBoy

2074 posts

Uber Geek

ID Verified

Lifetime subscriber

#2709456 19-May-2021 08:30

We have a large attic space above the living areas and study. The roof is rafters where the insulation and intello wrap sits. So the entire attic space is inside the thermal envelope. That is going to end up being the plant room effectively. HWC, MHRV and heat pump unit will live in there.

timmmay

20581 posts

Uber Geek

Trusted

Lifetime subscriber

#2709462 19-May-2021 08:35

SumnerBoy: We have a large attic space above the living areas and study. The roof is rafters where the insulation and intello wrap sits. So the entire attic space is inside the thermal envelope. That is going to end up being the plant room effectively. HWC, MHRV and heat pump unit will live in there.

Nice. Ducted heat pumps are pretty loud, you'll want to make sure you have a good amount of insulation between the heat pump and the living space, and locate it as far from lounge / bedrooms as you can. Also ask if it can be mounted on rubber to absorb vibration. Our current one was put over my sons bedroom and it sounds like a truck idling outside.

Ducted heatpumps aren't the panacea that some think they are. Highwall units are more appropriate in many situations.

SumnerBoy

2074 posts

Uber Geek

ID Verified

Lifetime subscriber

#2709464 19-May-2021 08:38

Hmm, yeah I am still in two minds. I am leaning towards ducted because the heating and cooling demand should be fairly low so I envisage the system running at a pretty low speed for a low percentage of the time, to keep things ticking along.

Seems easier to manage as a single unit rather than 3 different hiwalls..

timmmay

20581 posts

Uber Geek

Trusted

Lifetime subscriber

#2709470 19-May-2021 08:52

SumnerBoy: Hmm, yeah I am still in two minds. I am leaning towards ducted because the heating and cooling demand should be fairly low so I envisage the system running at a pretty low speed for a low percentage of the time, to keep things ticking along.

Seems easier to manage as a single unit rather than 3 different hiwalls..

The main problem we have with a ducted units without individual room control is the north facing rooms get much warmer than the other rooms. We've turned the damper down so when it's heating the room doesn't get super warm, but that means when it's cooling it doesn't cool the room much and the other rooms get much cooler. Automatic damper control is the ideal and main solution, but if you want to be messing with a control panel every day to manually enable and disable heating / cooling per room that's an option. I wouldn't have a ducted unit without individual room control unless none of the rooms get direct sun. I just had one ducted heating unit removed (it took 2 days to install and 4 hours to remove) and have another ducted with an Airtouch going in late June. I kinda wish I'd just leaf the highwall in the lounge and oil heaters in the bedrooms. We just wanted the wall space back and to remove the oil heaters, it's costing $13K plus wall repair.

With high wall units you put one in each room, an RM Pro controller somewhere in the room, and control it using the app.

Quic Broadband

Move to New Zealand's best fibre broadband service (affiliate link). Free setup code: R587125ERQ6VE. Note that to use Quic Broadband you must be comfortable with configuring your own router.

SumnerBoy

2074 posts

Uber Geek

ID Verified

Lifetime subscriber

#2709504 19-May-2021 10:22

Here is the layout of the house - it is facing NW. The ducted unit is going to sit in the attic space above the lounge/study and have ducts into the open plan living/dining/kitchen/lounge (x2), study and master.

As you can see all areas being serviced by the unit are on the same side of the house so should have similar requirements in terms of heating/cooling - aside from the size differences.

Initially I was just going to have a hi-wall unit above the lounge facing into the kitchen/dining/living to ensure the main living areas were warm/cool, but the architect is worried about overheating in the study and master.

timmmay

20581 posts

Uber Geek

Trusted

Lifetime subscriber

#2709601 19-May-2021 12:34

That looks fine to me. I would want a zoned system for efficiency, say I just want to have the office heated if I'm working from home.

Why is architect worried about overheating? You can change the air volume through each duct using a damper, so the office damper might be set at 20%, master bedroom at 30%, and multiple outlets in the kitchen / dining each set to 100%. That will probably work ok, not as good as Airtouch and automatic damper control. I'd personally go for the Airtouch or at least a zoned system with manual on / off controls for each zone.

SumnerBoy

2074 posts

Uber Geek

ID Verified

Lifetime subscriber

#2709603 19-May-2021 12:41

Mainly due to the large amounts of glazing on that side of the building. And the fact it is air tight and super insulated. I will be looking to put in low-solar gain glazing on those windows to reduce the overheating, but that comes at a cost since you don't get the same solar gains in winter when you want it.

I just got a quote for the 4 zone controller from Mitsi - around 3k for 4x dampers, controller and install. Waiting to hear back from Airtouch but have requested a quote. Or I could just get the dampers installed and control them via a 24V signal myself apparently...

timmmay

20581 posts

Uber Geek

Trusted

Lifetime subscriber

#2709606 19-May-2021 12:56

I considered DIY damper control, but by the time you add up dampers, controllers, etc, and your time I don't think it's worthwhile.

I'd probably try to avoid solar gain altogether and rely on heating you can control, so reducing heat from sun is fine.

Kickinbac

427 posts

Ultimate Geek

#2709789 19-May-2021 18:17

SumnerBoy: We have a large attic space above the living areas and study. The roof is rafters where the insulation and intello wrap sits. So the entire attic space is inside the thermal envelope. That is going to end up being the plant room effectively. HWC, MHRV and heat pump unit will live in there.

Sounds like you need to find Matt Risinger on YouTubes if you haven’t already. He is the building science nerd and loves a good attic plantroom with MVHR etc.

Also look at external shading options for the rooms you think may overheat.