4 ms·

A shower heat recovery system would be better, which seems like such low hanging energy saving I am unsure why it isnt more of a thing.

brewsmithy 4y ago
There are a couple reasons waste heat recovery has not been adopted in the US anyway. The designs up to this point have been adaptations of industrial designs, not specific designs for residential use.
pja 4y ago
A neighbour has one of these. What surprised me was that it didn’t bother (as far as I could see) pulling the heat out of the waste water - it was setup to pull the heat out of the air in the bathroom. I guess this makes at least some sense though? A sizable proportion of the heat from shower water must go into water vapour that evaporates into the air as the droplets fall from shower head to floor drain. If you go into an unventilated room where someone has had a shower & you’ll find the air both very warm & very damp! Using a heat recovery system like this also means you don’t need to pull cold dry air into the bathroom from outside in order to avoid condensation problems - the heat recovery also pulls the water out of the air - so it saves a considerable amount of energy that way too. Whether these are enough to offset the installation cost I don’t know.
- shapefrog 4y ago
  The ones I designed in my head, that it turns out exist in the real world, exchange heat from the drain water to warm the cold water flowing to the shower, reducing the usage of hot water (https://zypho.uk/ https://zypho.uk/ for example - turns your 10 deg C cold flow to 20 C from the 40C waste flow) In winter one would like the hot humid air from the bathroom to be heat exchanged and heat dumped back into the property. In summer perhaps feed the input airflow for a water heat pump and again dump out the humid air. Either way, we leave a lot of efficieny the table.
  - theluketaylor 4y ago
    Drain heat recovery is quite common here in Canada and mandatory in a few jurisdictions for new builds. https://www.homedepot.ca/en/home/categories/building-materials/plumbing/water-heaters/drain-water-heat-recovery.html https://www.homedepot.ca/en/home/categories/building-materia... As for the hot humid bathroom air, that also exists in the form of ERV (energy recovery ventilators). For well sealed houses you route all the exhaust and intake for the home to one place where there is a heat exchanger to minimize the losses from getting fresh air into the house.
- SuoDuanDao 4y ago
  there's probably also the benefit that condensing the water out of a post-shower bathroom will dehydrate the air, reducing mold/rot issues in the house.

brewsmithy 4y ago

There are a couple reasons waste heat recovery has not been adopted in the US anyway. The designs up to this point have been adaptations of industrial designs, not specific designs for residential use.

pja 4y ago

A neighbour has one of these. What surprised me was that it didn’t bother (as far as I could see) pulling the heat out of the waste water - it was setup to pull the heat out of the air in the bathroom. I guess this makes at least some sense though? A sizable proportion of the heat from shower water must go into water vapour that evaporates into the air as the droplets fall from shower head to floor drain. If you go into an unventilated room where someone has had a shower & you’ll find the air both very warm & very damp! Using a heat recovery system like this also means you don’t need to pull cold dry air into the bathroom from outside in order to avoid condensation problems - the heat recovery also pulls the water out of the air - so it saves a considerable amount of energy that way too. Whether these are enough to offset the installation cost I don’t know.

shapefrog 4y ago
The ones I designed in my head, that it turns out exist in the real world, exchange heat from the drain water to warm the cold water flowing to the shower, reducing the usage of hot water (https://zypho.uk/ https://zypho.uk/ for example - turns your 10 deg C cold flow to 20 C from the 40C waste flow) In winter one would like the hot humid air from the bathroom to be heat exchanged and heat dumped back into the property. In summer perhaps feed the input airflow for a water heat pump and again dump out the humid air. Either way, we leave a lot of efficieny the table.
- theluketaylor 4y ago
  Drain heat recovery is quite common here in Canada and mandatory in a few jurisdictions for new builds. https://www.homedepot.ca/en/home/categories/building-materials/plumbing/water-heaters/drain-water-heat-recovery.html https://www.homedepot.ca/en/home/categories/building-materia... As for the hot humid bathroom air, that also exists in the form of ERV (energy recovery ventilators). For well sealed houses you route all the exhaust and intake for the home to one place where there is a heat exchanger to minimize the losses from getting fresh air into the house.
SuoDuanDao 4y ago
there's probably also the benefit that condensing the water out of a post-shower bathroom will dehydrate the air, reducing mold/rot issues in the house.