A new research confirms:
Balcony glazing saves energy

Savings of up to 10.7% and, on average, up to 5.9% in the residential building's heating energy consumption. - These outstanding results were obtained by Kimmo Hilliaho in his research on the balcony glazing's energy-economic effects completed in August 2010 at the Tampere University of Technology.

The research was conducted in Finland and supplemented with reference calculations obtained from Germany. The heating energy consumption of glazed and unglazed balconies was compared with each other by using field measurements and computer simulations. In addition, it was ascertained how the balcony type, thermal insulation and the direction affect temperatures inside glazed balconies.

New, efficient windbox

The results show that taking compensation air from a glazed balcony clearly increases energy savings arisen from glazing. In the best case, the balcony functions as an efficient windbox, which makes it possible for the balcony-owner to reduce the temperature by one degree in the room behind the balcony. Thus the residents can save energy and improve their housing comfort.

If installed for recessed balconies, the glazing is often a more efficient energy-saver that the glazing installed for protruding balconies. The savings for south-side balconies are slightly higher than those for balconies facing towards other directions. However, the savings gained by both types are substantial. The study of glazing tightness revealed that larger gaps between balcony glass sheets didn't much affect energy saving levels.

Crucial is how the residents use their balcony glasses. In most cases, the Finns know the energy-economically best way of using balcony glazing: glasses are kept closed in winter and open in summer. However, the provision of more accurate directions is necessary to maximise savings.

Even higher savings obtained in Germany

The research was supplemented with energy calculations implemented in such element houses in Berlin that were comparable with the Finnish houses under research.
Heating energy savings gained with the use of balcony glazing varied in Berlin from 5.6% to 12.0%. The glazing was most beneficial to buildings with balconies facing towards south and compensation air taken through the balcony. Taking supply air from the balcony instead of taking it directly from outside was the factor that had the most distinct impact on energy savings. On average, heating energy savings in Germany amounted to 8.2%, which is even more than in Finland.

A solution that pays off

Keeping the building base in good condition and its management costs on a reasonable level have a direct impact on housing costs - and satisfaction of the residents. In addition to housing comfort, the top-quality and properly used balcony glazing provides the residents and owners with pure financial benefits.

The conclusion drawn on the basis of the research results published in Tampere was clear: it is advisable to provide especially the multi-storey buildings built in the 1960s and 1970s with balcony glazing. Substantial savings could also be obtained in new multi-storey buildings with a compensation air intake through the glazed balcony.

In addition to energy savings, the balcony glazing could bring about other significant economic benefits. According to the research made by D.Sc. (Tech.) Jussi Mattila, providing balconies with glazing has an impact on the general condition of the house: it may even postpone the renovation need of balconies in the building from six to ten years!

» The summary of the study in English (page 3)

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Professor Matti Pentti's comments on the study

From research to practical conclusions

"The research results can be utilised directly in many different ways," sums up Kimmo Hilliaho. -"Balcony glazing allows property owners to postpone facade renovations for several years, save heating energy and reduce operating costs.

The results provide grounds for architects to plan semi-warm space to be used as green zones between the yard and interiors. It is also well-grounded to include energy-saving glazing solutions in such renovation plans that aim at reducing energy consumption.

For those who invest in balcony glazing, the information about energy savings and better structural conservation makes their procurement economically viable.

It is now possible to provide planners and permit authorities with studied information of energy savings most of which are gained with supply air intake through a glazed balcony."

All in all, the investment pays off

"It wasn't any surprise to get new research results as a proof of 5% energy saving effects arisen from balcony glazing," states Professor Matti Pentti from Tampere University of Technology. "The glazing keeps the balcony a couple of degrees warmer during heating periods, which reflects upon inside temperatures. Eliminating the impact of wind is very important, too. It was a foreseeable result as well to learn that the glazing protects structures. We had already access to research results gained by D.Sc. (Tech.) Jussi Mattila of the glazing's protecting effect on concrete structures.

The annually longer operating time, comfortableness and space addition offered by the glazed balcony should also be considered in the assessment of investment profitability."

Great outlines: the whole concept

"It is advisable to start the search for better energy-efficiency from the desks of planning authorities and architects already," emphasises Matti Pentti. "Ideal plots are planned with a view to building homes and houses with large sitting room windows facing towards south and small bedroom windows towards other directions. The purpose is to get protection against wind while letting the sun warm up the space in winter.

It is best to plan facades so that the glazed section covers larger areas. This solution has lately somehow slipped out of the mind of those concerned. The glazed balcony is without heating and the glazing as such does not change it to interior space, which would affect the building permit application.

As noted in the discussion on the flats' energy savings, the question is of better insulation, water supply fittings, energy-efficient household appliances, energy-saving lamps, temperatures inside the flats, ventilation etc. In most cases, heat recovery refers to the use of technical systems. According to the research, outer space that benefits from direct sunlight is an efficient heat recovery option as well.