GROUP 1 - BUILDING ENVELOPE

- Positioning on the site
- Window orientation
- Area efficiency
- Walls, floors, Roofs
- Doors
- Windows

Positioning on the site

The building´s positioning on the site should aim at reducing the exposure to wind and the resulting cooling effect from winds sweeping the envelope. Solar radiation should be generously made use of in the heating season, and avoided in the hot parts of the year. Unwise use of glass must be avoided. Such planning grips do not cost money. The planners just needs to be careful and apply knowledge.

Window orientation

Earlier studies have shown that the heating need increases by 20% annually in a dwelling with most windows facing North (away from the sun) as opposed to dwellings where they face all opther directions than North. The passive solar heating through wondows is hence valuable.

Through windows natural daylight also enters the spaces innside. Wise use of windows can reduce the need for electric lights during daytime.

Area efficiency

Good planning resulting in rational space use per function leads to efficient compact buildings, Such area efficiency reduces both the investment (reduced m2) and the yearly running costs (energy bills).

Floor, Roof, Walls (Gulv, Tak, Vegger )

In low energy dwellings the bulding envelope Must have a very high insulation standard. To reduce heat losses considerably the walls will be up to 30 cm wide, floors 25 cm and roofs 35 cm. But for every cm wall thickness increase (inwards) one reduces the usable intermal area of a typical sized dwelling unit by 0.5 m2.

The construction must be airtight. The wind must not penetrate the construction. Cold bridges must be avoided. Special attention must be given to corners, wall- and roof openings and the joining of wall/roof and wall/foundation. Construction methods that reduces the volume needed of construction materials should be considered.

Beyond a certain standard there is little gain in excessive insulation.
The building industry´s earlier increase from for example10 to 15 cm insulation resulted in a heat loss reduction of 0.11 W/m2K. An increase from 25 to 30 cm will only result in a reduction of 0.02 W/m2K. It is hence uncertain if extreme insulation will become widespread.

The better we insulate, the more important avoiding cold bridges becomes.

Dust condensation can occur on internal walls in well insulated buildings. This is caused by dust being attracted to the cold bridge and can occur as light strips on the wall for each 60 cm where the wall structure is. This can be avoided by using construction materials with broken cold bridge.

Other advice

• The sleeper/foundation joint is often uneven and results in leakages.
• The top of the foundation must hence be even.
• The roof and floor holes for the chimney must be considered.
• The sides of the chimney must be even and straightened to avoid air leakeges. og rettes,
• The wind barrier must not be perforated by electricla cables, tubes and water pipes. All perforations should be planned and carried out carefully. Wind barreirs must be tightened around all perforations. Glue or use of timber battens to press tight is useful.
• Technical rooms plasseres sentralt i huset for å redusere kabel og kanalstrekklengder. should be centrally located to minimize lenths of cables and hence perforations.
• Avoid bay windows and recesses as these create unneccesary large cooling areas as a result of corners and joinmts that are difficult to get airtight.
• Recessed windows can create cold bridge challenges if windows are positioned in block walls that have insulation in the middle.
• Remember radon barrier towards the ground and ventilate radon out.

For more information go to the internet and search for sites of relevance using keywords like : building envelope, insulation standard etc. Then add your country or region behind the search word if you prefer local products.

Doors

Doors are holes in well insulated walls. They loose up to 10 times more heat per area than walls or roofs. They also can leak a lot of air. A well insulated door with good gaskets is hence important.

A separate entry space or foyer is a good wind breaker that avoids cold air from entering the inner rooms. However – if the door is not well insulated it cools down the entry space and good insulation standard is necessary in the entry space´s walls and ceiling to avid it impacting the other rooms ina negative way. A well insulated door is therefore important regardless of solution.

For more information go to the internet and search for sites of relevance using keywords like : door manufacturers, door manucaturers association, door insulation etc. Then add your country or region behind the search word if you prefer local products.

Windows (Vinduer)

Windows are, like doors, heat loosers, although slightly higher insulation standards in windows haveresulted in increased use of glass in buildings. U-values under 1.1 W/m2 K is preferable. The energy saving is considerable when instead of using two layers of sealed glazing or old two layers glass in double timer frames (3.0 W/m2K) one uses two layers with Low Emission (LE) film one one side and timber frames ( 1.60 W/m2K). Even better is the saving if one goes for super insulated windows with two layers of glass ( 1.1 W/m2K). All these options are commercially available. In order to reach insulation standards of 1 or 0.85 W/m2K – three layers of galss is necessary.

When the glass units becomes large (area) and the more layers of glass they have, the heavier each unit becomes. Moving them around gets complicated and heavy tools necessary.

When using three layers of glass as opposed to two also the ingoing solar radiation is reduced for each layer of glass.

External rime on windows with high U-value in well insulated buildings is not an acceptable reason for complaint. The pheonomenon occurs only a few days a year and predictable since it is wether and temperature dependent. The cause is this :
External radiation towards the sky (vertical) on clear nights, mostly in the morning.
It results in windows that one cannot see through while the phenomenon occurs.
It can be avoids by using a canopy over the window that is rolled down the night before to reduce the radiation on such days.

Windows in sloped roof can let in up to 30 % more light per glass area than wall mounted windows.
The reason is that obstruction from neighbouring buildings, trees etc has less impact on windows in sloping roof than in vertical windows. Overheating through roof mounted windows is a challenge though.

For more information go to the internet and search for sites of relevance using keywords like : window manufacturers, window manufacturers association, window insulation, energy efficient windows etc. Then add your country or region behind the search word if you prefer local products.