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Keep the heating in a house all day on?

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Vovk_Z:

--- Quote from: Zero999 on October 27, 2021, 01:59:27 pm ---I don't see how anyone could consider 15°C to be cold,

--- End quote ---
The Earth needs more people like you. As for me, any inside temperature lower than 22 C is cold (in autumn/winter). :) (because of cold external wall, small but cold droughts).

Alti:

--- Quote from: Siwastaja on October 27, 2021, 12:58:12 pm ---Short RC indeed improves controllability, but for a high cost: small R means high loss of energy. Insulation slows down adjustments but quite obviously reduces the consumption.
--- End quote ---
Increasing R reduces the consumption, at a cost of raised investment, quite obviously. Had you been offered an R for free - go for it. However, keeping same R for two houses with vastly different RC constants and using them for N-th part of the time (lets say RC1>>RC2,  N=1 / N=2 examples), the second house would require half of the energy of the first one. So instead of investing into raising R, you can invest into lowering RC, reaching same total costs. In this sense, I disagree with the quote.

I'd rephrase: Heating well insulated house 24/7 costs same as heating a not so well insulated low RC house occupied 1/N-th of the time. Whether this tie is for N=1.1 or N=13 for specific design is a different story.

SiliconWizard:
Depends, of course, as said above, on various factors.

One thing in favor of heating at all times is managing humidity. RH can be pretty high indoors during fall and winter in the absence of heating, depending on where you live, the kind of house, etc. This can be nasty.

Of course, if you go for constant heating, you can set it for lower temperatures when you're away. Just enough to manage humidity levels and make it reach a comfortable temperature in just a few minutes when you get home.

langwadt:

--- Quote from: Marco on October 27, 2021, 01:36:21 pm ---Homes built with below slab insulation and minimal above slab insulation will have too much thermal mass to get to a comfortable temperature from cold in a reasonable time frame.

--- End quote ---

well, it should also mean that it stays at a comfortable temperature longer

Siwastaja:

--- Quote from: Alti on October 27, 2021, 07:14:21 pm ---
--- Quote from: Siwastaja on October 27, 2021, 12:58:12 pm ---Short RC indeed improves controllability, but for a high cost: small R means high loss of energy. Insulation slows down adjustments but quite obviously reduces the consumption.
--- End quote ---
Increasing R reduces the consumption, at a cost of raised investment, quite obviously. Had you been offered an R for free - go for it. However, keeping same R for two houses with vastly different RC constants and using them for N-th part of the time (lets say RC1>>RC2,  N=1 / N=2 examples), the second house would require half of the energy of the first one. So instead of investing into raising R, you can invest into lowering RC, reaching same total costs. In this sense, I disagree with the quote.

I'd rephrase: Heating well insulated house 24/7 costs same as heating a not so well insulated low RC house occupied 1/N-th of the time. Whether this tie is for N=1.1 or N=13 for specific design is a different story.

--- End quote ---

Yes you are right, and as a consequence, houses that are not constantly occupied do not require as much insulation, it would be money wasted. This holds even in very cold climates. It's an easy thing to do if duty cycle is a few % and the period is a month (for example, spending weekends somewhere once a month).

Now the question is what to do when duty cycle is say 50% but period is as short as 24hrs - people live in the house but go to work and so on.

Because given cold enough climate - Canada or Northern Europe for example - amount of insulation absolutely needed to make the houses liveable without exploding heating costs pretty much forces the RC time constant in the range of a few days or more, which then prevents optimizing on a 24hrs cycle period, but still allows doing that with longer cycle (holiday reduction, etc.).

But really, the equivalent circuit is parallel RC with a current source (heating supply) feeding power into it, voltage being room temperature. Small R (poor insulation) seemingly increases controllability giving the false impression that you can save energy by "dropping" the temperature, but in reality that drop is caused by wasting the energy so you are not saving anything compared to having higher R.

Except, as you mention, high R has an investment cost, you do save by not having to invest into insulation materials and thicker walls and more expensive windows and so on. This is a classical optimization problem which can be performed in Excel quite well.

In my opinion, designing buildings that last for a long time is the best idea. When building, insulating properly is not that big of an extra expense and it pays back within the first decade or so, and generates savings for the next 50-100 years. I don't like the idea of buildings lasting for only 30-40 years.

Retrofitting insulation is a significantly higher expense, usually.

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