Heating requirements for the winter garden?

A conservatory has, due to its usually four external walls (including the roof) and their significantly lower thermal resistance, a multiple of the heat demand of a living space with solid walls. Therefore, for energetic reasons, a conservatory should also remain unheated.

Can one roughly estimate the heat demand of a wood-aluminum conservatory with approximately 90m³ enclosed volume that is lived in?

30m² floor area, about 41m² post-and-beam construction, 35m² roof area, all with 1.0 glazing. Posts 5x12/16cm (corners 16x12cm), beams 5x10/16cm, rafters 8x20cm, purlin 14x34cm, all spruce glued laminated timber.

Many thanks in advance for a brief information on how much higher the heating energy demand is compared to a similarly sized living room built to old or new construction standards?

Surely no one is familiar with it. At least no one who has read it, I count myself among them as well.
Best regards and hope you get help, unless you have already sought advice at the hardware store or specialist shop!?

Hello Sebastian,

thank you very much for your reply. Unfortunately, I have not received any answers to any of my postings here in the house construction forum so far... What a pity... My questions probably do not fit here very well... but it was worth a try. Do you know a good forum for conservatories and for building physics?

I had the conservatory calculated. According to this, it requires a heating output of 2800 watts at an assumed outside temperature of -12°C and a room temperature of 20°C, plus a reheating surcharge for occasionally heated rooms. Thus, the heating load is about 3 times as high as a room in an uninsulated old building.

Well, heatable does not mean constantly heated...

Best regards

Maddin

Hi Maddin

I don’t think you are wrong here. There is probably just no one here who has the same problem and/or knows about it.

I can’t name another forum for you, I only signed up here.

Just wanted to suggest to read your post again, maybe someone will be found after all.

Regards

about heat demand in the conservatory?

Hello Maddin,

- often the difference between the heating capacity to be installed (based on the maximum demand, without solar gains, outside temperature -14 to -16 ° depending on location) and the heating energy demand/consumption is blurred. The heated conservatory is not a priori an "energy guzzler" compared to a solidly built room. This applies especially during peak load times, e.g. New Year's Eve party, -20° outside temperature. I have already drunk coffee with my family in the conservatory on a bright sunny day in January, -10°C outside temperature, wearing only a shirt, without any heating. Taking into account solar gains, a drastic shortening of heating days or heating hours, there is even a gain relative to the usable area of the house, especially if you can close the doors to the living room on cold winter nights. More precise calculations have been published, for example, by Prof. Marquardt (Buxtehude) on the internet and in specialist journals. Of course, you can calculate the peak demand for your conservatory. However, please note that with conservatory-specific heating, the arrangement also matters (heat source at the coldest spots and not where the heating installer just finds the nearest pipe) and for the peak capacity case also the necessary dimensioning (approx. 300-350 W/m² of usable area) and that the panes need good air circulation so that after fogging due to rapid temperature/humidity changes they can dry quickly again. You can of course also choose from the start not to spend nights in the conservatory at low outside temperatures, then a lower heating capacity is sufficient. But then later, if you have forgotten this decision, don’t blame the conservatory builder or the heating installer if the glass box does not get warm.

Have fun planning—and even more with the finished conservatory!

Spenke

Hello Spenke,

thank you very much for the link. The conservatory has been standing for a few years now and I can only confirm your experience. It’s something special when you’re sitting at the coffee table in a T-shirt while outside people are trudging through the snow in thick winter coats at -10°/-15°...

But exactly for the scenarios you described (Easter, Christmas, New Year’s Eve, birthdays) we want to be sure that we can use the conservatory independently of the sun. Heated doesn’t mean "constantly heated," but for this use we are dependent on the peak heating load...

As mentioned, the heating load calculation came out to 2800 watts for 30 m². However, that corresponds to less than half of the 300-350 watts per m² you specified... which is correct?

We have trench heaters along the glass surfaces, but why do so many planners actually recommend underfloor heating in the conservatory?