ᐅ Chimney: Inside or Outside Location?

Hello,
we are currently planning the renovation of a masonry barn that has long been used as a wood storage and workshop, and earlier partly as a livestock stable and grain storage. With all the opinions from various building professionals around me, my head is starting to spin; so I hope to get some independent opinions here :-)

We have basically finalized the floor plan with our architect; but now the question came up as to why we are planning to place our wood stove in the living room with a flue pipe running outside along the house wall, instead of designing an internal flue pipe.
So far, I have only seen an advantage in having an external chimney because it supposedly prevents thermal bridges to the roof and is probably less expensive.

Am I missing something? Would an internal chimney flue actually be more advisable, even in our case? And if so – for what reasons?
The stove is basically meant to just make the living room cozier (visually and, of course, thermally in winter) and is not intended to heat the entire apartment in any way.

Here are some basic details about the building project in case relevant:
Floor area approximately 230 sqm (2,475 sq ft)

• 2 floors: ground floor = basement (already existing), living area on the 1st floor (slab already in place)
• Roof will be torn down and rebuilt, but without usable attic space, i.e. probably as a cold roof with nail-plated trusses and metal roofing; insulation will then be in the ceiling towards the living area. An alternative of a sandwich roof was also discussed. This will be clarified in the next few days.
• Heating: gas heating or heat pump (probably the latter), with solar thermal and photovoltaics

If you need more information beforehand, feel free to ask... Thanks in advance 🙂 🙂

Hello,
do you mean those stainless steel chimneys when you say external chimney pipe? Many people simply don’t find them visually appealing. However, I do think they can look quite good on some houses if well designed. But that’s a matter of personal taste. They are indeed generally somewhat more affordable.

A masonry chimney (which is usually built inside the house) can be very well insulated and possibly used for a second flue for a gas boiler.

Regarding heating:
current prices per kWh: gas 4 cents, electricity 20 cents.

So unless you buy a heat pump with a _guaranteed_ COP of at least 5, you will lose money.

And achieving a COP of 5 is hardly possible even with a ground-source heat pump. From an economic perspective, only gas heating really makes sense here.

Best regards,

Andreas

Thank you! If there are no issues with the exterior installation aside from the appearance, then that’s probably the one we’ll choose.. 🙂 We both actually quite like the style.

The heat pump would only be an option in combination with a photovoltaic system. Also, I assume that the gas price will increase over the next x years since it is, after all, a finite resource.
In the long run, that would make it economical again. Or am I missing something?

Your architect should be able to advise you in more detail about the chimney. It depends on many factors, and ultimately it has to suit your preferences.

Heating: No, currently there is no calculation that makes a heat pump economically viable. In recent years, the gas price has generally been decreasing while electricity prices have been rising. That’s why heat pumps are often artificially favored in energy saving regulation calculations, whereas gas heating systems are rated less favorably. For a new build, if you want to install a gas heating system, you usually have to incorporate either a mechanical ventilation system with heat recovery and/or a significant amount of solar thermal collectors to be allowed to use gas heating. Whether your renovation falls under these (new build) regulations can certainly be confirmed by your architect.

A heat pump also requires a very low supply temperature, which means you need either underfloor heating or very large surface collectors (radiators).

A photovoltaic system won’t benefit your heat pump much at first. Heat pumps require 400 V / three-phase power, while the photovoltaic system usually delivers 240 V / two-phase power. That doesn’t match... Also, you need the heat pump mainly in winter, when the photovoltaic output is minimal.

Best regards,

Andreas

Since a ventilation system is sensible anyway, gas plus ventilation still counts as the more affordable method. Any possible price fluctuations over many years are purely speculative and often exaggerated to cause fear.
And keep in mind: choosing gas today doesn’t mean you won’t switch to electric heating in 20 years. The other way around is more difficult, as you would first have to install a gas connection, possibly digging up half of your front yard, etc. 🙂
For me, an air-source heat pump means heating with electricity. For those without a gas connection in the street, this technology offers a great, innovative solution! Those with gas connections can generally get by more cheaply with gas.

We placed our fireplace inside the house because, in my opinion, this stainless steel option is more of a retrofit solution than something to plan from the start. It’s the same with built-in roller shutters immediately after completion. They look makeshift and not intentional.

These are very good points regarding gas, thank you Payday!
Did you encounter any problems with insulation in the ceiling/roof with your chimney option?