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Re-using the heat in bathwater in Britain

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Re: Re-using the heat in bathwater in Britain

#51

Post by cameronh90 »

Someone1234 wrote: post #21
wcoenen wrote: post #7

I tried this once on a cold winter day: I let the bath cool down to room temperature (which was <20C) before letting it drain, with the bathroom door open. The result was a lot of condensation on the windows in the surrounding rooms. I figured the high humidity was going to cause more damage than it saved money, so I scrapped the idea.

Although higher humidity should make it feel warmer given the same ambient temperature. So if you're increasing the temperature mildly using this method AND increasing humidity, it may compound one another positively. Although, it is a minor efficiency gain either way.

I'm in the UK, extra humidity is the last thing I'd ever want in winter.

At the moment, I've got two beefy dehumidifiers running and I'm still at between 70-85% humidity in each room. I don't have any damp or leaks, it's just that the outdoor humidity has been 80-90% for the last few weeks, so ventilation is futile. And because of the weather at the moment, we're drying clothes indoors.

Re: Re-using the heat in bathwater in Britain

#52

Post by Anthony-G »

wcoenen wrote: post #7

I tried this once on a cold winter day: I let the bath cool down to room temperature (which was <20C) before letting it drain, with the bathroom door open. The result was a lot of condensation on the windows in the surrounding rooms. I figured the high humidity was going to cause more damage than it saved money, so I scrapped the idea.

As a bather, I also tried this idea a couple of years ago. I thought condensation would be an issue but the house I live in seems to have low humidity. The bigger downside for me was having to expend more time and effort cleaning the sides of the bath.

This summer, I tried taking cold showers as an alternative energy conservation measure. So far, this Autumn has been very mild in Ireland so I've been able to keep up the habit (I still treat myself to a bath once a week or so).

Re: Re-using the heat in bathwater in Britain

#53

Post by ArmandGrillet »

Tangentially related: has someone found something less energy intensive than taking a bath while bringing the same degree of warmth?

I've been looking at heated blankets but they're all made of polyester which is not comfortable due to the moisture being trapped under the blanket. Heated seats in some cars are the closest sense of comfort I've found but that technology doesn't seem to exist for regular seats.

Re: Re-using the heat in bathwater in Britain

#54

Post by HPsquared »

yrgulation wrote: post #22

Energy poverty can be sorted out by better insulation and investment in cheaper and more sustainable sources such as nuclear, wind and solar. Instead of working around this issue with clever hacks this needs to be a national policy. I think all roofs should be mandated to have solar panels installed, as a start, and all new builds should have proper insulation.

If I was planning national energy infrastructure, I wouldn't plan on dividing the equipment into a million tiny pieces and installing it on roofs, of all places. It seems much simpler to manage a solar farm than 10,000 roofs.

Re: Re-using the heat in bathwater in Britain

#55

Post by skrause »

wcoenen wrote: post #7

I tried this once on a cold winter day: I let the bath cool down to room temperature (which was <20C) before letting it drain, with the bathroom door open. The result was a lot of condensation on the windows in the surrounding rooms. I figured the high humidity was going to cause more damage than it saved money, so I scrapped the idea.

Living in Germany and getting both my heating and hot water from natural gas I regulary track my gas consumption throughout the different seasons. With 1-2 showers per day in the household my daily natural gas consumption in winter is about 20x higher than in summer, so compared to heating the house the energy in the hot water is a drop in the bucket.

Re: Re-using the heat in bathwater in Britain

#56

Post by cameronh90 »

newaccount74 wrote: post #44
bausgwi678 wrote: post #24

Earlier quoted context omitted.

It depends massively on your climate and how air in your house is managed. If you live somewhere which is significantly colder outside than in (e.g. 0-5C out, 21C inside) heating outside air to comfortable temperatures will greatly decrease humidity. Couple this with a system which circulates air, or even exchanges inside&outside air and you will have incredibly low humidity inside. I live somewhere which often sees…

Ventilation with heat recovery sounds like it could work in those conditions, but just barely. 80% @ 15C would turn into 55% @ 21C.

Unfortunately, very few homes in the UK have any air ducting. I'm looking at installing a MHRV system at the moment, but planning the ducts is a nightmare. Brick walls, lintels and structural joists everywhere with no headroom between floor and ceiling.

We absolutely should be doing it in new builds though, and we're not.

Re: Re-using the heat in bathwater in Britain

#57

Post by hgomersall »

sweettea wrote: post #6

Not discussed: hot water in houses increases humidity. In modern well sealed houses, that can result in unfortunate mold growth.

It's because the house builders don't do the job properly and install MVHR, which not only removes the excess humidity, but also recovers most of the energy of vaporisation.

Re: Re-using the heat in bathwater in Britain

#58

Post by zubspace »

ArmandGrillet wrote: post #53

Tangentially related: has someone found something less energy intensive than taking a bath while bringing the same degree of warmth? I've been looking at heated blankets but they're all made of polyester which is not comfortable due to the moisture being trapped under the blanket. Heated seats in some cars are the closest sense of comfort I've found but that technology doesn't seem to exist for regular seats.

Maybe just one or two hot water bottles? [1] We use them in Winter to warm our feet in bed. But they are very versatile and can also be used to alleviate any kind of tension.

I also use one while I code: I put it inside of a small (baby-)sleeping bag wrapped around my feet. Sounds weird, but it's so comfortable!

[1] https://www.google.com/search?q=hot+water+bottle&tbm=isch

Re: Re-using the heat in bathwater in Britain

#59

Post by GavinMcG »

ArmandGrillet wrote: post #53

Tangentially related: has someone found something less energy intensive than taking a bath while bringing the same degree of warmth? I've been looking at heated blankets but they're all made of polyester which is not comfortable due to the moisture being trapped under the blanket. Heated seats in some cars are the closest sense of comfort I've found but that technology doesn't seem to exist for regular seats.

https://solar.lowtechmagazine.com/2022/01/the-revenge-of-the...

Re: Re-using the heat in bathwater in Britain

#60

Post by hgomersall »

yrgulation wrote: post #22

Energy poverty can be sorted out by better insulation and investment in cheaper and more sustainable sources such as nuclear, wind and solar. Instead of working around this issue with clever hacks this needs to be a national policy. I think all roofs should be mandated to have solar panels installed, as a start, and all new builds should have proper insulation.

Waste water heat recovery should be mandated. I'm not sure if you included that in your "clever hacks", but it's definitely fantastic value for effort.
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