Manufacture of wooden houses - House insulation

House by the lake - preparations before the leak test

House by the lake was designed to be a passive house, i.e. a very energy efficient house. No more than 15 kWh/m² per year should be consumed to maintain it, as required by the passive house standard. This means very good thermal insulation and minimising air exchange with the outside, which is done with energy losses. After the walls were raised and the roof was built, the team Litarh must now ensure that it is very well insulated and that the connections between roof and walls, walls and ceiling, windows and wall do not allow air to pass in any direction. How well and accurately this work has been done will be seen in the airtightness test. Preparations for this test can be followed in the video at the end of the article. Those who have not yet seen the Josephs' journey to this point of the work can watch here the other episodes.

Litarh house by the lake

Why do the leak test

To achieve the energy performance level of a passive house, the principles of construction are as follows:

  • very good thermal insulation,
  • as few or no thermal bridges as possible,
  • high-performance window,
  • airtight envelope verified by leak test,
  • quality indoor air with a ventilation and heat recovery system.

Air exchange with the outside depends on how well the envelope is executed. The components of the envelope are the walls, roof, windows, doors, foundation, which must be linked together so that there is no air exchange with the outside. If the thermal insulation is very good, with quality materials and a thick continuous layer, and if windows that meet passive house requirementsThese air exchanges are the only culprits of heat loss in winter and heat gain in summer. Sealing means closing off any places where air could enter or leave the house uncontrollably.

Checking the airtightness of the tyre is done with the airtightness test or blower door test which tells us how much air is lost from the house in a given time and where. Many of the losses are found at component joints and penetrations for electrical or water-to-water paths.

Sealing is done with special membranes

Sealing the house is done with the help of foils that are continuously fitted inside. Continuous means that they must cover the inside face of all walls, roof, ceilings and the concrete floor slab (that bubble the design engineer talks about in the film). In design there is the pencil rule that says that on a section of the house project, you must be able to pencil over the seal coat without lifting it. Sensitive areas are around doors and windows, balconies that have exterior decking, penetrations for mounting utility runs. For a perfect seal, attention should also be paid to the joints between the sheets. They are overlapped and taped with special adhesive tape.

These films are called vapour barrier films. They are membranes that are put on the side of the house insulation to prevent moisture in the air from passing through and condensing on the back wall. They are different from the anti-condensation films that are put on the roof, on the outside of the insulation. This protects the insulation from moisture that might otherwise reach it.

The separation between the anti-condensation film and the vapour barrier is done by a factor called vapour permeability Sd, expressed in metres. It represents the equivalent vapour permeability of a layer of air of the same thickness. Membranes with Sd2m are vapour barriers.

Final works for the perfect sealing of the Lake House

The erection of the Lake House is nearing completion and final checks are being made on the joints. Design engineer Constantin Tudosă, representing of the builder Litarh, explains below what work has been done to make the house as close to ideal as possible. Next, the leak test will prove it. It's an intermediate test, done precisely to find any leaks early on and fix them. At the end of all the work, when the house is ready, the test is repeated. But how this test is done and what the results should be for a passive house, in the next episode.

About the author

Mihaela Radu

Mihaela Radu is a chemical engineer but has a great passion for wood. She has been working in the field for more than 20 years, wood finishing being what defined her during this period. She gained experience working in a research institute, in her own company, as well as in a multinational. She wants to continuously share her experience with those who have the same passion - and more.

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