Introduction

 

 

Nearly 50 percent of the world’s energy need is for the building sector, if including production of building materials, transport to site, construction, energy need during the building’s life and the demolishing of buldings.

The energy efficiency potential in the building-sector is considerable. Most countries have to import energy at huge costs.

In the western world we now see the contours of more effective energy systems where the same service can be supplied with far less energy than before.

Energy labelling of buildings is about to be introduced throughout Europe.

Planners, contractors and clients might hence as well adjust to the demand of tomorrow. That will give them a competitive advantage.

 

Fact

In the North European climatic zones, energy need for housing is typically 15.000 – 30.000 kWh per year.

U-values based on today`s standard building regulations are then :

  • Walls 0.22 W/m2 K (200 mm insulation.)
  • Floors,Roofs, 0.15 - (275 mm nsulation.)
  • Windows 1.60 - (Double glazing, LE film and timber frame)

Energy need split (kWh) in typical North European Climates :

  • 60% for space heating (9.000 – 12.000 kWh per year).
  • 20% for DHW (3.000 – 4.000 kWh per year).
  • 20% electric lights and household appliances (3.000 – 4.000 kWh per year).
  • Sum 100% (15.000 – 20.000 kWh or 150 – 200 kWh/m2/year. Detached housing is higher.)

In more Southern climates the heating need is replaced by huge cooling needs. These could be covered by electrically based cooling units or – better – by passive means in combination with electric based cooling.

Dwellings with half energy need and where all extra investment costs are covered over time by reduced energy bills are now being built throughout Europe.

It is possible also to build dwellings where the demand for energy is reduced to one third of today`s standard. However its is mainly the need for heating which is reduced and the need for DHW and electricity can not easily be reduced that much. Due to this, the energy need split is changed. In such houses termed ”passive houses” the ”new split turns out to be like this :

  • 15-20% of the energy need is for space heating (1.500 kWh or 15 kWh/m2 per year).
  • 60% for DHW (4.000 kWh or 40 kWh/m2 per year).
  • 15-20% electric lighting and household appliances (1.500 kWh or 15 kWh/m2 per year).
  • Sum 100% (7.000 kWh or 70 kWh/m2 per year. Detached housing is higher).

U-values are then :

  • Walls 0.10 W/m2 K
  • Floors,Roofs, 0.08 – 0.10
  • Windows 0.75 – 0.95
  • External doors 0.80

So we choose to go even further. Definitions :

  • Passive house standard means energy need below 15 kWh/m2 per year for space heating alone.
  • Low energy house is defined as a dwelling unit which needs less than 100kWh/m2 per year totally.

It is relatively uncomplicated to reach a level of 150 kWh/må per year totally in new buildings.

But it is very demanding to get down to 50 kWh/m2 per year in new buildings.
Consideable efforts are to be made also to reach 115 kWh/m2 per year in existing buildings.

In order to plan low energy houses one need knowledge about the products that can be part of the packages that in sum result in the energy efficient and smart buildings.

On this web site the criteria for choosing building components that can be part of such a package are described. Insteda of making the issue into a whole science, we have tried to simplify it so that as many as possible can grasp the key issues.

In simplifying, some unclarities might arise. Neither the authors nor the web site operator or host or others involved can take any responsibility for the consequences of the free information and advice presented here in good faith.