The Traditional Maintenance-Free House is part of a large development project: The MiniCO2 Houses. The project involves a total of six detached houses, each of which illustrates various aspects of reducing CO2 emissions in the construction, use and maintenance of a house.
The Maintenance-Free House focuses on “maintenance and service life” and examines how much CO2 can be saved when a house is built to have a service life of at least 150 years, and the building envelope needs no maintenance for the first 50 years of that service life. House A – described here – has been constructed using traditional materials, which have proved their long service life, and House B has been constructed using new materials, which are expected to have a long service life.
Maintenance-Free House A has thus been constructed in accordance with building techniques which have proved their longevity over centuries. The main material is red brick, i.e. clay that has been dug from the ground, formed into bricks and fired, and then built brick upon brick with mortar – as houses in Denmark have been built for almost 1,000 years. The house has glass doors, full-height windows and a tiled hip roof. The house rests on a plinth which functions as a covered veranda protected by the roof's generous overhang all the way around the house.
Inside, the Maintenance-Free House has been designed as a living organism with spatial niches, pockets, recesses, short corridors, intermediate zones, etc. In its design, the house has something of an urban setting about it – with the common room as an open space; the open, light and airy atmosphere with high ceilings, where it is possible to look from façade to façade and from gable to gable; and with the bedrooms as intimate and embracing buildings intersecting the streets of the town and open space.
Robust and simple solutions for familiar problems
The house is especially supported by two key elements, which serve to bring a wide range of benefits: An interlacing masonry wall and a generous overhang roof.
• The exterior masonry walls are of solid brick, constructed without the use of vapour barrier or insulation. The inner and outer leaves are interlaced: large clay blocks form the inner leaf, interlocked to the outer brick leaf by header bricks. The inner leaf insulates by having a multitude of small cavities; the outer leaf of traditional bricks is laid in half stretcher bond with interlocking headers to the inner leaf. The traditional bricks ensure a maintenance-free and long-lasting outer surface.
• Building the masonry using a single type and size of brick provides long-term protection. Different materials will move differently with temperature fluctuations, and over time this often leads to cracking with subsequent damage. The simple wall, on the other hand, moves uniformly and is not prone to damage.
• The use of brick and a simple masonry construction without vapour barrier creates a diffusion-open wall. It can absorb and discharge moisture thereby balancing the humidity – producing a healthier indoor climate.
• The weight of the wall enables it to store heat during the winter and cold during the summer, enabling it to compensate for temperature fluctuations between day and night – again for a better indoor climate.
• The interior surfaces consist of clay block, walls are finished with a filler, some clad with wooden panelling; all surfaces which do not require ongoing maintenance in the form of paint, etc.
• The roof has been designed as a collar roof without penetration of the roof surface. It is steep, so that water flows away quickly away, thereby minimising the risk of water damage.
• The insulation in the roof is of paper wool, which has good moisture-wicking properties, making the use of vapour barriers superfluous.
• The roof has an overhang – approx. 1 meter wide – on all four sides. It protects masonry, doors and windows giving the building envelope a good basis for actually lasting for 150 years without requiring maintenance during its first 50 years.
Reducing carbon emissions
Carbon emissions from the materials used for the life cycle of the design of the Traditional Maintenance-Free House are in line with a normal average house: the Reference House (both have been calculated at 5 kg CO2/m²/year for a 50-year period). In other words, ensuring the housing a longer service life and fewer maintenance demands has not been at the expense of carbon emissions.
The long service life may result in the house lasting at least twice as long as a normal house. In that case, of course, the savings will be substantially greater.
In the Maintenance-Free House A, the replacement cost of materials over five years is calculated at approx. 0.4 kg of these 5 kg of CO2 compared with approx. 0.6 kg of the 5 kg in the Reference House. The carbon-saving effect of low maintenance is therefore not in itself remarkable. This is because the most carbon-intensive building elements such as foundations, glass and mineral wood insulation rarely require maintenance, whereas the parts that can normally require replacement during the course of the house's service life – doors, windows, interior surfaces, etc. – are relatively "light" in a CO2 context. It is evident, however, that this – admittedly modest – share of carbon emissions is nevertheless 30% less than that of the Reference House – pointing to the effect of a good overhang and robust surfaces both outside and in. But it is also worth bearing in mind that for the owner of the house, low maintenance on these elements means less frustration – and cash savings on workmen and materials.
The large number of bricks in the Maintenance-Free House means that the external walls in particular account for much of the carbon profile. Although the roof structure also includes a large tiled areal, the CO2 contribution is not huge – because the roof also incorporates a large amount of CO2-binding wood, both for the loadbearing structure and for the fixed sub-roof. In addition, paper wool has been used for ceiling insulation.
All in all, the results show that if construction and design – as performed in the Maintenance-Free House A – lead to an extended service life for the house as a whole, they will reduce carbon emissions over the total expected service life.
The MiniCO2 Houses development project
The Maintenance-Free House is one of six demonstration homes built in the coastal town of Nyborg in central Denmark. Five of the houses examine various ways of reducing carbon emissions; the sixth house brings these experiences together.
For many years, the efforts of the building industry to reduce CO2 emissions – not without reason – have focused on energy for heating and therefore also on airtightness and insulation. However, as national and EU building requirements become ever stricter in this area, it becomes relevant to examine how the industry can also reduce carbon emissions – for example, in terms of materials and of user behaviour.
The main objective of the MiniCO2 Houses development project is thus to reduce CO2 emissions in the construction, operation and maintenance of a house.
The six houses share the same overall principles:
• Building type: Single-family detached home
• Size: 130 to 172 m²
• Energy guidelines: Danish 2015 Standards
• Budget: Normal economy
• Architectural design: Broad appeal
• Future: Sale of the house after completed experiment
↧