Impact on Choice of Appliances

It goes without saying that if the integrity of the thermal envelope is a critical part of a passive house, then consideration must be given to appliances that might breach this envelope. Additionally, the PHPP model takes into account the energy usage and output of the appliances being used in the house, together with the number of people living there, to ensure that the certification criteria of “renewable primary energy demand not to exceed 60 kWh annually for all domestic applications (heating, cooling, hot water, and domestic electricity) per square metre of usable living space”.

So appliance selection is important!

Most modern appliances are energy efficient, so replacement of your existing appliances is only actually needed if they are old and inefficient, or if they will breach the thermal envelope, such as a drier ventilation or a range hood extractor. Fortunately there are modern versions of both these appliances that are self-contained within the house – recirculating range hoods and heat-pump or condenser driers.

We opted for Miele appliances throughout, but many other brands also offer suitable appliances at lower cost. We spent a lot of time searching for a dedicated recirculating range hood before we realised that many models can be converted by simply adding a device within the vertical column. As can be seen from the photo below, at the top of the vertical column are grills and it is out of these that the air flows back into the room having been filtered for grease and odour.

It is really important that you have good quality filters to prevent grease from going into the ventilation system. For us it was also important to have charcoal odour filters as our kitchen is an open plan room with the living.

We opted for a heat-pump drier that has a tank into which the extracted water flows and which is then manually emptied between each cycle. You can get these plumbed in, but that was even more cost that we didn’t wish to incur! It is staggering to me to see the amount of water that is extracted from a load of two bath towels – close to 4 litres! (and that is after a good strong spin cycle in the washing machine!) I see so many houses in my area with a drying rack sitting in the window area with the windows closed, and I just think of all that moisture that is being put into the house and how bad it must be for the health of the occupants.

We also have an old-school drying rack in the laundry (and a washing line outside) so we don’t use the drier more than a few times a week. The drying rack is incredible and the ventilation system extracts moist air and circulates the air gently, and so overnight a load of washing can be dry without putting the moisture back into the house. We know several people who have built passive houses and don’t have a drier at all for this reason.

Note that we have a solar PV system with battery and so use “free” energy to power the drier. Without the solar power we perhaps would have been more reticent about getting a drier due to the environmental impact of the energy usage.

The choice of our other appliances was not influenced by living in a passive house. The energy demand requirement might mean that if you have a hobby or business activity that requires significant energy demand, you might have to take that into consideration, but for us the only “high draw” appliance we have is the steam shower. However, as this is not a daily use appliance its energy demands did not have a big impact on the PHPP modelling. In fact, we still have quite a lot of leeway in our energy demands, which is useful as we are going to install an active heating/cooling appliance for the extreme parts of the year (more abut that, and our reason why in a future post!).

Don’t forget that your appliances generate heat, even when in stand-by, and this heat is important in the ambient temperature within the house.

5 comments on “Impact on Choice of Appliances

  1. Hello,

    Thanks for sharing this whole proces with us.
    What an amazing journey.
    Is everything working out the way you expected ?
    A question, has it been a very costly exercise or is it true it is about $17.000 more than building a traditional house?
    Will reread this many times and hope to build a passieve house one day.

    Thanks,
    Pien

    • Hi Pien. Gosh, that’s such a hard question to answer! I would say that overall everything is working as expected. We definitely do need some form of active heat/cool to provide boost in the extreme situations, and that was something we hadn’t understood properly. I will write a post about that sometime. It will definitely cost you more than just an additional $17k if you want to achieve certification. If you want to adopt most of the principles but not go to the degree of having triple glazing etc, you can probably get away with spending $20k more than a standard build (This is a guess and is not very scientifically arrived at!).

      • To be clear, it costs a lot more to build a certified passive house over a standard code-minimum build, which is why most people don’t do it. Just off the top of my head, the extras include thicker framing, significantly more insulation, airtightness membrane, heat recovery ventilation system, full slab insulation, tripe glazing, PHPP modelling, blower-door testing, and certification. I would estimate at least 20 per cent more if comparing homes of comparable size.

  2. Did you find any dedicated recirculating rangehoods (ie carbon filter based) within NZ? I’m struggling to find any

    • Hi Debbie. Thanks for your interest. You should look at the German brands as passive house is more established in Germany. Or brands from countries where there are lots of apartments as apartments often can’t have ventilation to the outside, especially if the building is old. We got a Miele one. The recirculating kit is an extra (about another $90). What I learned is that the range hoods are not explicitly advertised as “recirculating”, it’s just by reading the detailed specs that I learned that some can be modified. I hope that helps!

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