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Bruno da Costa, Mitesh Pareck and Toby Flaye

(242 - user rating)


Passive House + Sunspace = Flexible + Sustainable

The Sunspace is a type of greenhouse that is embedded 3.5m into the ground. The concrete walls are angled to catch solar gain and the passive house is set back far enough to allow the optimum light in order to obtain maximum plant growing

Why the addition of a sunspace?

Passive houses are too rigid. There is little or no flexibility of space. Our main design decisions were driven by the notion that the future requires flexibility and an ability to sustain yourself.

Once you have built your regular passive house, it is finite - additions and repairs will only damage and compromise the air tight shell. This is especially true of pre - fabricated factory made versions; once they have been assembled on site there is no way to adapt.

Sustainable living has many forms and the ability to grow food throughout the whole year is a concept that would have major ramifications to how you shop, store and eat (especially as the plants and where they grow have many added benefits).

The third aspect was the mounting costs and inability to source triple glazing in Bulgaria. As a reaction to this we minimised the use of triple glazing and used it as a last resort only (when the light from the south was not enough). There are a small number of small windows on the west and east wall and one on the south above the sunspace. It is cheaper to source twice the amount of double glazing. Therefore using two layers of double glazing to create a buffer zone in which you can grow plants and give yourself flexible space.

Reuse wherever possible

The cooker is fitted with a recycling air extractor with a carbon filter which cleans the air but not extracts it – this is done by the HMVR which includes this into the heat exchange.
Biogas digesters have been fitted to break down all human and plant waste – which will produce 1.71m3 biogas a day. Enough to supply the daily cooking need and help heat the hot water boiler occasionally.
Solar pipes are fitted to the roof (although facing north) in order to provide hot water throughout the summer months.

Internal Flexibility

This design promotes both internal and external flexibility through the use of the sunspace. Used daily the sunspace will be cooler and fresher in the mornings as the plants will oxygenate the air. The sunspace will then get hotter than the passive house in the afternoon allowing the excess heat to be included in the HMVR system and contributing to the passive house’s passive heating.

The addition of the sunspace does not negatively affect the enclosed passive house. The enclosed passive house still remains a constant 21oC and has a complete air tight seal. The sunspace provides an option to enjoy a controlled environment.
Our calculations show that the sunspace will not remain as constant as the passive house but will regulate a between 19oC - 24oC – this is because of its depth underground, the included thermal mass of the basement and the added plant life. The heat and condensation which will accumulate at the top of the sunspace is incorporated into the condensation catcher (grey water system) and MVHR system.

Also the use of sliding partitions on the ground floor (which has thermal mass) which enable the user to adapt the position in order to suit the user’s requirements. If they want to create more shade then slide the partition across to block out the sun, if they want to heat up a different part of the house in the evening (using the partition as a thermal sink) then exposing the partition during the day will do the trick.

With flexibility comes control and it is paramount that the user is in full control of the environment in which they live.


The sunspace is a truly flexible space because of its external shading. A sliding, lightweight, timber frame runs along the full length of the southern glazed façade. The bottom 2.5m of the frame is distributed with shelves. Upon which the user can plug in the plant pots of their choice (the plant pots that live in the sunspace over winter). The higher portion is a trellis which enables the established and perennial vines to flourish throughout summer and then die back over winter.

The distribution of shelves and trellis has been calculated to achieve optimum shading potential during the different seasons.

The sliding frame retracts in winter and slides under the protection of the stationary frame – distributed in the same way the stationary frame juts forward past the house in order to shelter the carport and the eastern façade of the sunspace.

This ever changing façade allows the user complete control over the amount of daylight entering the sunspace (regulating its temp) and their passive house (regulating its solar gain and temp)

Passive House

The passive house is set back from the site constraints and we decided that the south façade needed to have maximum solar gain in order for the sunspace / shading system to have full potential. Therefore the house is positioned in order to not be shadowed by the neighbouring houses.
When approaching from the east (the road) you enter the drive and onto the gravel up to the car port – which is sheltered by the stationary shading frame. In front of the car port is the first glimpse of the sunspace – the eastern glazed façade is un-shaded in order to encourage the morning sun into the basement. The rest of the east façade is predominantly clad black timber – with only three exceptions – two small windows (for the two toilets) and the front door.
After gaining entry you will notice the double height space afforded along the whole south side of the house. The bathroom is to your right and the stairs leading to the basement on the right next to the bathroom. The sliding partitions obscure the views to the kitchen but the views into the sunspace and out the back (west) into the garden beyond will draw your gaze.
The south and west side of the house have whole walls of glazing. These are buffered by the sunspace. The kitchen is open plan and very bright because of its exposure to the outside.
As you walk past the kitchen and through the live space you twist back up the stairs and head to the first floor. There are two very simple bedrooms – both with north facing, triple glazed windows and the main bathroom at the end. Each room has a secondary source of light – a double glazed window facing south into the double height space and the other triple glazed window at the top of the house (on the south wall).
As you walk down the stairs to the basement you are surprised by how much light is reflected down here. The full extent of the greenery will become clear – the sliding doors here allow you to open up the room if you want. The services and plat are hidden underneath the stairs. Here you will find a washing machine, centrifuge dryer, the hot water storage and the grey and black water tanks and a biogas digester directly below the two toilets.