[Retric]

That’s an artifact of how heating is setup inside your home. Which is more efficient depends on where you’re dumping heat inside the home, levels of insulation, etc.

Energy moves from hot to cold linearly with temperature differences. Hypothetically, if the pipe was the same temperatures as the inside of your home all the heat transferred would be outside the envelope. The hotter the pipe the better this ratio becomes. This is true regardless of what percentage of the pipe is inside the envelope.

However, heating along the exterior of the home under windows and such then you’ll heat the exterior walls to higher temperatures than the interior thermostat thus losing more heat to the outside. Radiant heating on the other hand largely avoids this effect.

[looofooo0]

Look at ISO 7730, a lot of comfort comes from non-cold walls and their radiant heat and small difference of wall temperatures to air temperatures. So having a thoroughly heated home allows you to lower your air temperature. Apart from that modern gas and even more heat pumps greatly gain efficiency by lowering flow water temperatures.

[aesh2Xa1]

Having read that document, the ISO 7730 model itself depends on stable temperatures. However, I think the key is simply to understand thermal mass; people can be in hotter air, but feel cold due to cold surfaces (e.g., floors or furniture), which heat more slowly (or lose heat more slowly) than the air itself.

Therefore, 1st: Heating/cooling cycles from your HVAC are fighting these objects because they don't mix at the same speed as other objects (e.g., the air itself), so you end up with gradients across objects; people rate this feels unpleasant.

2nd: Mechanical equipment tends to operate more efficiently under constant load compared to constant start and stop cycles.

With #1 and #2, you can just heat constantly to increase both the uniformity of heating across objects and also the efficiency of the mechanical equipment's energy conversion.

There's a 3rd point, which, really, is just a sneaky way of reframing #1 and #2, and that is that you can also lower your setpoint and still have a subjectively superior comfort perception compared to a cyclic system. It drives home the point to say "constant 68F feels more comfortable than intermittent 72F." But it also invites the complaint about constant versus intermittent energy use, right? So I think just detailing #1 and #2 is better.

[looofooo0]

https://www.krantz.de/wp-content/uploads/2024/04/layout-spec...

[aesh2Xa1]

That spec aligns with my understanding, including the model's dependence on comfort perception. I was, initially, in disbelief about it, but changed my mind after reading thru. The texty reply was to make it more palatable for someone like me to accept. I think we agree.

One thing I missed in summary is the concept of general radiant temperature gradient. It's not only about the gradient for conduction, but for radiation (and convection). So you could probably improve my summary by talking about any gradient between different objects in the environment and their EM, which feels unpleasant (but I think it had value in its reduction of the problem, too).

[Retric]

It’s a deep rabbit hole as condensation, humidity, etc also enter the picture. Efficiently lowering temperatures for sleeping further complicates things.

That said, heat loss is through exterior surfaces so you really want to avoid spot heating of poorly insulated exterior walls. Thus the design of baseboard heaters can make a larger impact than you’d think.

[looofooo0]

Baseboard heaters need very high temperatures. I would not recommend installing this anywhere. Having big Typ 33 heaters for temperatures below 45°C will greatly increase efficiency of your heating system. Otherwise, a split air con is also an efficient way of heating.

[sokoloff]

Baseboard heaters are often sized such that very high temps are needed (because that's what cheapest/lowest labor/least space used), but they don't have to be sized that way. In the attic bedroom, we have baseboards around the entire perimeter on two walls and same in the bath. I run the attic zone on the same water temp (outdoor reset controlled to be quite low) as the rest of the house (mostly large cast iron rads, one cast iron convector). Good insulation and air sealing in the attic means that the attic zone calls way less than the downstairs.

[looofooo0]

Which is not exactly efficient. 40C or less is desirable.

[sokoloff]

My return water temps are 115F (46C) on a P98 design heating day, and obviously cooler on warmer than design days. Cooler is always better, but "baseboards require 180F [82C] water because that's what's on the spec sheet" is a commonly-held but mistaken belief.

[DamonHD]

I moved all my radiators away from under windows (and upgraded the windows to triple glazing) to avoid maximising the temperature differential and energy loss through the wall under the windows, while eliminating the cool drafts that the under-window radiator placement was intended to counter.

[Benanov]

Radiators were originally designed to heat more than needed, so you could open the windows.

In New York, at least - the standards were never changed to accomodate for closed windows in 1920. Snopes has a rundown. https://www.snopes.com/fact-check/apartment-radiator-pandemi...

[organsnyder]

My house (built in 1916) was insanely over-provisioned. When we upgraded to a modulating-condensing boiler, we halved the BTUs and are still able to easily keep the house heated to any desired temperature even on the coldest winter days.

[sudahtigabulan]

Do you mean you moved them to another wall, or just increased the gap?

(not a native speaker here)

[DamonHD]

Moved them to another wall.

Eg: https://www.earth.org.uk/note-on-superinsulating-bedroom.htm...

[HPsquared]

What do you do for ventilation?

[DamonHD]

The windows all still open, but in winter we have (nearly) enough MHRV (Mechanical Heat Recovery Ventilation) not to need to ventilate directly, eg see:

https://www.earth.org.uk/MHRV-mechanical-heat-recovery-venti...

[DamonHD]

I'm really confused about (not complaining, just not understanding) the downvotes.

These are statements of neutral fact, and the whole process is described in some detail on my site, for each room that we retrofitted.

I don't understand if I have caused offense or something: apologies if somehow so!

[joncrocks]

I'm not sure, but I think that the reason that radiators are placed near windows (at least historically) was to avoid hot/cold spots in rooms.

By placing the radiator near the place that is likely the coldest place in the room, you ensure that the room is an even in temperature as possible. Rather than to counteract 'cool draughts'. I think.

So perhaps people thought that your initial comment was wrong/misleading.

But if you have triple glazing and this mitigates the heat loss, then the coldest wall of your room may no longer be the one with a window, so you may well be doing the right thing for your room(s).

[DamonHD]

Even if the coldest wall is still the exterior one (it should be, thermodynamically), best maintaining comfort in the room need no longer be by pumping heat out through that wall (or window) to reduce thermal gradients in the rest of the room. Those residual gradients (and, eg, cold drafts down those cooler exterior walls) can be small enough to not need fixing any more.