Once again, a question that keeps bothering me. We are currently renovating an old farmstead and cannot reach a conclusion regarding the interior insulation.
The current wall structure consists of two rows of old fired bricks. Don’t stone me, but our architect’s documents say 30cm (12 inches), though I believe it’s actually less, around 24cm (9.5 inches). I can measure again tomorrow if needed, but I don’t think it affects the question.
Recommendations from the architects regarding interior insulation:
Architect A: Fired brick -> lime plaster -> 20cm (8 inches) Multipor insulation -> lime plaster
Architect B: Fired brick -> lime plaster -> 6cm (2.4 inches) air gap -> insulation (e.g., mineral wool) -> Ytong or sand-lime brick, both layers anchored -> lime plaster
The latter option is attractive for us because we could also improve the structural stability at the same time and compensate for the leaning of one wall (10cm (4 inches) over 225cm (89 inches) height). However, I now read in almost every forum only arguments against option B and in favor of option A.
What exactly is the difference compared to new cavity wall constructions? They are built similarly, just with a facing brick and, of course, not with a thickness of 24cm (9.5 inches). According to the calculation on ubakus, the dew point is between the walls in both cases. In the case of Multipor, it absorbs the moisture and slowly releases it again when it is drier or the room is ventilated properly. How does this work with option B? The air gap would need to be ventilated, or where should the condensate go?
This topic is really getting me down. Especially since these are two architects, both of whom have renovated many old buildings, and they recommend two completely different approaches. …can’t they just agree :p
The current wall structure consists of two rows of old fired bricks. Don’t stone me, but our architect’s documents say 30cm (12 inches), though I believe it’s actually less, around 24cm (9.5 inches). I can measure again tomorrow if needed, but I don’t think it affects the question.
Recommendations from the architects regarding interior insulation:
Architect A: Fired brick -> lime plaster -> 20cm (8 inches) Multipor insulation -> lime plaster
Architect B: Fired brick -> lime plaster -> 6cm (2.4 inches) air gap -> insulation (e.g., mineral wool) -> Ytong or sand-lime brick, both layers anchored -> lime plaster
The latter option is attractive for us because we could also improve the structural stability at the same time and compensate for the leaning of one wall (10cm (4 inches) over 225cm (89 inches) height). However, I now read in almost every forum only arguments against option B and in favor of option A.
What exactly is the difference compared to new cavity wall constructions? They are built similarly, just with a facing brick and, of course, not with a thickness of 24cm (9.5 inches). According to the calculation on ubakus, the dew point is between the walls in both cases. In the case of Multipor, it absorbs the moisture and slowly releases it again when it is drier or the room is ventilated properly. How does this work with option B? The air gap would need to be ventilated, or where should the condensate go?
This topic is really getting me down. Especially since these are two architects, both of whom have renovated many old buildings, and they recommend two completely different approaches. …can’t they just agree :p
N
nordanney22 Feb 2021 22:43South schrieb:
20 cm Multipor Really 20 cm (8 inches)? That easily meets passive house standards, and you’ll be cutting it close financially—triple digits per square meter.
South schrieb:
Now I’m reading mostly arguments against option B and in favor of option A in almost every forum. I see option 2 more often (though not monthly) in commercial buildings when the heritage facade must be preserved. In those cases, a "new" masonry wall with insulation is built on the inside.
As a non-expert, I wouldn’t immediately know why option B shouldn’t be used—if there is enough space for the thicker wall assembly.
Correction – it’s only 10 cm (4 inches) 😉
Thank you for the follow-up question. I had actually assumed 20 cm (8 inches) and only asked architect A again after your question. She has been advising us so far and also developed the rough renovation concept.
Option 2 will probably not work for us (unfortunately), as the wall would have to stand on our already completed new concrete slab, which, according to the architect, is not designed to support walls or loads of that magnitude.
Both architects agreed, however, that we should leave the uneven exterior wall as it is. It is part of the house’s character, and the tilt apparently does not have any negative structural consequences, provided we eliminate the identified weak point. This weak point is a cut middle purlin. The previous owner had apparently shortened it to make room for the attic conversion. We will support it again and additionally install another purlin between the middle purlin and the base purlin. I hope this will solve the problem.
Also, instead of floor-to-ceiling windows, we will only slightly extend the historic window openings (by about 25 cm (10 inches)). That way, the unevenness will be less noticeable visually (4 cm (1.5 inches)), and enough light will enter the area anyway through the fully glazed 3.00 x 3.00 m (10 x 10 ft) barn door. The masons and carpenters are expected to agree on the door details.
I hope this will be a good long-term decision.
Thank you for the follow-up question. I had actually assumed 20 cm (8 inches) and only asked architect A again after your question. She has been advising us so far and also developed the rough renovation concept.
Option 2 will probably not work for us (unfortunately), as the wall would have to stand on our already completed new concrete slab, which, according to the architect, is not designed to support walls or loads of that magnitude.
Both architects agreed, however, that we should leave the uneven exterior wall as it is. It is part of the house’s character, and the tilt apparently does not have any negative structural consequences, provided we eliminate the identified weak point. This weak point is a cut middle purlin. The previous owner had apparently shortened it to make room for the attic conversion. We will support it again and additionally install another purlin between the middle purlin and the base purlin. I hope this will solve the problem.
Also, instead of floor-to-ceiling windows, we will only slightly extend the historic window openings (by about 25 cm (10 inches)). That way, the unevenness will be less noticeable visually (4 cm (1.5 inches)), and enough light will enter the area anyway through the fully glazed 3.00 x 3.00 m (10 x 10 ft) barn door. The masons and carpenters are expected to agree on the door details.
I hope this will be a good long-term decision.
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