Log cabin from 1999, question about energy efficiency

  • Erstellt am 2023-09-11 13:58:15

-LotteS-

2023-09-11 16:16:29
  • #1


But there is a lot in between...
We even achieve KfW40 with our new log house: 10cm square spruce log | 20cm cellulose insulation | 6cm exterior cladding also made of spruce boards. But for that, you also need XPS under the slab, more insulation in the roof, and so on.

Do you know the manufacturer of your desired object?
 

WilderSueden

2023-09-11 20:29:06
  • #2
In theory, yes. In practice, it is sometimes omitted during high demand. In this respect, you should already have a pretty good chance of actually seeing it now. But make sure to get an energy performance certificate, as a consumption certificate makes little sense for weekend houses.
 

n_hardt

2023-09-27 20:46:28
  • #3
Thank you very much in advance for the many responses. I have now received the further data.
Wall construction:
Massive block beams made of Finnish pine, evenly dried, cleanly planed, and provided with a double tongue and groove profiling. A flexible sealing compression tape, applied layer by layer in the block grooves, serves as additional sealing. The special joints are carefully sealed with felt tapes. The sapwood areas of the exterior walls are additionally stabilized with a threaded rod.
- Block beam 95 mm x 170 mm;
- Wind protection paper:
- Slip rail construction (45 mm x 95 mm) for accommodating the mineral fiber insulation (100 mm)
(other insulation available on request and for an additional charge);
- Vapor barrier;
- Block panel cladding (20 mm x 170 mm).

Roof construction:
- Pine wood panel with tongue and groove, 15 mm thick;
- Solid pine finishing strips (wall/roof slope);
- Vapor retarder;
- Laminated purlins made of Finnish pine according to structural calculations;
- Blocking boards between rafters including felt tape sealing, mineral fiber insulation (200 mm) on site;
- Rough boarding with tongue and groove as a rainproof, breathable, and windtight underroof;
- One layer of bitumen insulation felt on site;
- Counter battens (24 mm x 48 mm);
- Roof battens (24 mm x 48 mm);
- Eaves boards (20 mm x 170 mm);
- Eaves soffit boarding (15 mm x 95 mm) for an additional charge.

Windows:
Window and door openings receive special reinforcement that on the one hand accounts for the settling of the log house, but on the other hand structurally strengthens these openings. The box double windows made of Nordic pine according to Finnish standard in primed finish include triple glazing with muntin variation, as well as ventilation wings with mesh inserts.

The kit supplier was Finn-Log
 

dertill

2023-09-28 08:39:16
  • #4

Results in a U-value of about 0.3 W/m²K -> New buildings until 2020 had less than 0.24 as a specification for individual component consideration. Old existing buildings range between 1 and 1.5 -> a good value without need for action, also in the long term. Should something ever be changed, the inner lining can be dismantled and the insulation replaced with better insulating material.

Also an energetically good construction here

Triple glazing with double box windows. Not only energetically good, but also looks good. The U-value should be comparable with new windows without double boxes.

With this construction, I would expect that the floor slab or under the screed was also insulated accordingly thickly, especially since underfloor heating has already been installed.
For 95 m², I would estimate about 6000 kWh heating energy demand.

Zfor recalculation / rough estimation for advanced users:

Transmission heat losses:
Volume = 2.8m * 95m²
Surface/Volume = 0.8
Average U-value of the surface = 0.3 W/m²K
Transmission losses at U-value 1 = 75 kWh / m²a
2.8m * 95 m² * 0.8 * 0.3 W/m²K * 75 kWh / m²a = 4,788 kWh / a

Plus ventilation losses
:
2000 heating degree days (rule of thumb including solar heat gains, moderate climate)
Air exchange rate of 0.3 / h
Air volume of 95m² * 2.8m
2000 K*d * 0.3 /h * 24h/d * 95m² * 2.8m * 1.2 kJ/m³K = 4596 MJ = 1277 kWh / a


Additionally, there is hot water with about 500 kWh / year and person

The underfloor heating will probably not be designed for 32/28, but for 40°C supply at design temperature - but it could also already be 35°C.
If you then install a similarly suitable underfloor heating upstairs, nothing would stand in the way of switching to a heat pump with a high annual performance factor.

So purely energetically considered, recommended without restrictions.
 

n_hardt

2023-09-28 09:45:57
  • #5
Thank you very much for this super detailed answer! That all sounds really very good. My plan was also that underfloor heating should be installed upstairs and the whole thing operated with a heat pump.
 

Nida35a

2023-09-28 10:31:23
  • #6
An alternative would be to leave everything as it is and retrofit an air-to-air heat pump (split air conditioner) upstairs and downstairs as needed, add photovoltaic panels on the roof, and manage with very low heating costs for 9 months of the year. The gas heating would then only be a supplement for cold dark months. In Scandinavia, a lot is done with air-to-air heat pumps; the houses are designed for that.
 

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