Demo site 1. Borås and Varberg, Sweden

/Demo site 1. Borås and Varberg, Sweden
Demo site 1. Borås and Varberg, Sweden 2017-11-07T11:15:33+00:00

Building Name: “Forskningsvillan” house and Varberg house
Location: Borås and Varberg, Sweden
Status: In operation and monitoring since March 2014 (Borås) and June 2015 (Varberg)
Surface: 155 m2 each

Building use: (Borås) Full-scale test lab. (Varberg) residential
Building typology: Pre-fabricated wooden framed villas
Climatic zone: Continental

The Swedish demo site consists of two pre-fabricated low energy wooden framed villas.

One building is assembled in a new attractive residential area near Varberg. It was first used as display house for a time, and then, it became the family home.

The second building of the same kind is assembled at SP main research facility in Borås and used as a full-scale test lab for energy efficient technologies and construction details, with artificial user behavior loads. Different HVAC equipment performance are tested and evaluated, as well as impact of different user behaviors and construction details. The building is in parallel used for smart grid research and as a showcase for journalist and visitors.

The two pre-fabricated buildings are similar with a size of 155 m2 each. By means of the SP building, new materials were tested to increase the indoor comfort without increasing the energy consumption. Thus, the technologies evaluated in Borås, were then adopted and improved to the building in Varberg suited to the private user. The Borås demo will be certificated according to Miljöbyggnad level Gold (which is a Swedish certificate like LEED and BREAM) and the house in Varberg will meet the same criteria.

The strength of the construction of these houses will show how the future will deal with the issue of energy in private homes and strive for ZEB. Pre-fabricated villas are a mass market product. The house model developed is not a prototype, but a real solution to be a part of the standard catalogue of DEROME. It is constructed and equipped with energy solutions that will work in various climates and countries from Helsinki to Strasbourg, including UK, Germany and as well as other countries with similar climate.

> Demo site team: SP, DEROME
Derome Hus AB constructed and manufactured the houses in their facilities (sawmills, factory). Then the houses were assembled in the selected locations. SP Research Institute of Sweden contributed to refine the design and construction details and to ensure quality assurance of the assembly process. SP owns the house situated in their facilities in Borås which is used for research purposes.
Derome Hus want along with the SP under NEED4B raise awareness of future housing and develop the Nordic market to become more energy efficient.

> Building process and schedule:
Architect’s work was one of the most important functions early in the project when the issue of design for maximum energy was of paramount importance. Then, a moist safe construction was done in the factory.

The “Forskningsvillan” house in Borås was finished in January 2014; The walls came in prefabricated elements which made the mounting time very low; in just two days the building elements were mounted and the envelope was sealed and water proof. This minimizes the risk of moist in the wooden construction from rain and mist. Three months later the house was finished. The monitoring equipment was activated in June 2014 and the behavior of a family of 5 members is simulated with energy loads.
The Varberg house was constructed in November 2014 and used as showcase until May 2015. In June 2015 a family of five members moved in the house and the measurement started.

> Main technologies and solutions

  • Building envelope: Loadbearing construction in wood. Climate shell with no cold bridges, wind protection and air/moisture safe. The new features of the building envelope concept are:

i) The placement of the windows in the middle of the wall and with the angled outside frame

ii) The concrete slab has a thin line of insulation under the sill to prevent water transport from the slab to the wall. The new solution of the construction of the concrete slab also minimizes the risk of radon gas leakage into the building.

iii) The intermediate floor attachment has extra insulation on the outside and is brought further in to the house to avoid a thermal bridge

iv) The roof insulation is partly put on the outside of the wood structure to prevent moist damages to the construction. It is a wooden construction with clay tiles. The new part is the insulation board outside of the wood construction and also a new type of roofing felt made of a material similar to GoreTex, called Isola.


Figure 1: New constructive solutions for thermal insulation of envelope against moisture;
  • Insulation:

i) Walls street side: Double skin facade

ii) Walls back side: Wall + 10 cm insulation

iii)Basement: Concrete +8 cm insulation

iv) Roof: Concrete +12 cm insulation.

v) Average U-value of 0.16 W/m2K, for total inside envelope area, including glazing, thermal bridges, etc. About 0.11 W/m2K for walls and 0.08 W/m2K for roof.

  • Windows: Windows glass with sun protection with a U-value of 0,7 W/m2 K. The Borås house has a control system for openings of windows.
  • Heating: The heat is provided by an exhaust air heat pump to a hydronic system. The heating uses electric power including for sanitary hot water production. The Borås house has a ground source and borehole heat pump COP 3.12 0/45º C that provides room heating and hot water.
  • Ventilation: Exhaust air recovery. A FTX-ventilation system (forced ventilation in all rooms with heat recovery). Ventilation rate of 0,35 l/s, m2 floor area
  • Lighting: CFL and LED lighting
  • Sanitary hot water: Low flow faucets, A+ dish washer, etc reduce demand. Heat is recovered with a shower drain heat exchanger. Solar collectors and the heat pump provide the heat.
  • Renewable Energy Sources:

i) PV panels: 14 modules IBC PolySol 260 W (23 m2) plus one inverter Sunny Boy SB 3600TL-21. The system is designed to be both economic and energy optimal for the type of house. Panels generate 3000 kWh/year

ii) Solar panels: Preparation for future addition of solar heating to the Boras house

  • Monitoring system: The measuring system in the Borås house is very advanced with over 100 measuring points and has a smart internal power grid. The Varberg house has oer 30 monitoring points. The equipment room houses all of the heating, ventilation, electrical and measuring system installations in the house. The electric system is connected in the equipment room with a 60 A fuse (larger than a common house to be able to simulate district heating for research purpose) and the inverter from the PV panels.
  • Other energy saving measures:
    • Entry porch preventing cold draft
    • Garden that utilize storm water
    • Semi insulated conservatory
    • Car port designed for integration of photovoltaic and charging station for electric vehicles
    • Energy efficient appliances (A++) Wooden framed construction (reduced “grey energy”)

In the Swedish demo site, one house is used as a full-scale test lab whereas the other is occupied by a five-member-family. Thus, SP will measure how the real family uses the house and compare it to the simulations in the Borås house. This will help to understand and improve the user behavior models for future research projects.

The house in Borås has over 100 monitoring points, and data measurement is ongoing since June 2014. The house in Varberg has 30 monitoring points, and started in June 2015.

Building performance and savings

Energy consumption values are expressed in terms of primary energy. Different conversion factors have been applied according to national or European standards:

Primary energy consumption

Breakdown of Energy Consumption in the building by type of measure (kWh/m2 year):

Heating Cooling Lighting Ventilation Domestic
Hot Water
13,89 6,53 10,61 31,03
Renewable Energy Sources Contribution (kWh/m2 year)
Heat from ground

Energy consumption values are expressed in terms of primary energy. Different conversion factors have been applied according to national or European standards:

Primary energy consumption

Breakdown of Energy Consumption in the building by type of measure (kWh/m2 year)

Heating Cooling Lighting Ventilation Domestic
Hot Water
27,21 2,84 22,05 52,1
Renewable Energy Sources Contribution (kWh/m2 year)
Heat from ground