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Karrinyup Residence

Status: complete

Services provided:
  • Architecture /
  • Design /
  • Interiors

The site that this home was built was very challenging. The property tapered from the front at 10m wide down to 5m wide at the rear. Narrow sites are challenging at the best of times but when the front of the property faces southeast it poses even more challenges. How do we get northern light into the center of the home to warm it in winter? How do we keep the sun out and the temperature down in summer? We overcame some of the challenges with the use of a central courtyard and stairwell. The central courtyard has a northeastern aspect, which allowed us to bring plenty of winter morning sun into the home. To keep out morning summer sun an adjustable louvred roof system was designed to be installed over the courtyard. At the time these images were taken our client had not installed the louvred roof. The building was performing very well without it and I believe to this day it still has not been required. This may seem odd looking at the pictures of the glazing around the courtyard but it is a great example where a client’s lifestyle is important to understand when designing a home. Our client’s just love opening up the bifold doors to this courtyard first thing in the morning and throughout the day in summer. They love the fresh air and warmth. A future family living in that home may find they feel the heat differently. It therefore may be more pertinent that the louvred roof system be installed to control the climate in that area. It should be noted that the current family living in the home don’t run their air conditioner except on the warmest still evenings.

Another reason the building stays cool is that the central stairwell acts as an extraction system for the home. By opening up the various louvred windows around the stairwell, the occupants can control the amount of air movements through this area. As air passes through the stairwell it sucks warm air out from other parts of the home. This home is essentially one half of a duplex pair. Both this property and the neighbouring property to the west share a common boundary wall. You would think that a two-story dwelling hard up against a common boundary would all but reduce any airflow. Behind the staircase there is a small drying court, four walls all of which surround it are two stories high. As air passes over the roofs of both houses and across the top of the courtyard, it essentially creates a low pressure system drawing air up and out through the courtyard. Air in turn is drawn through the house with an accelerated velocity. The whole system essentially works as a large exhaust for the home.

http://sustainabilityworkshop.autodesk.com/buildings/stack-ventilation-and-bernoullis-principle

This stairwell has the added benefit of becoming what is essentially a glasshouse in winter. Morning winter sun floods the area heating it and the polished concrete slab. In the evening this stored energy in the slab releases as the internal room temperatures drops, stabilizing the homes internal temperature.

The clients love timber flooring. Timber is an insulator so if you lay it over your concrete slab you lose a great deal of the benefit of its thermal mass. You simply can’t use the sun to heat up a slab that has an insulator covering it. We managed this aspect for our clients by maintaining a 1.2m strip of concrete before starting the timber flooring.

The construction of this particular home is double brick on a concrete ground slab to the lower floor, with timber stud frame on suspended concrete slab to the first floor. Double brick works fine on this home as the adjacent home to the west protects it from the worst of the afternoon summer sun. In any other location we would have looked at reverse brick veneer to provide the performance needed. Timber framing to the upper floor, where all of the bedrooms are located, was a conscious decision to reduce evening heat loading. The timber frame wall and roof system won’t store any heat so once the sun has set the rooms cool very quickly providing a comfortable space at night for sleeping. Thicker than usual studs were also used so we could get suitable insulation in the walls.

Sometimes during the design process our clients request certain things that may not necessarily be the best inclusions in a sustainable home. In this instance the clients wanted washed aggregate paving around the home and especially in the courtyard. You need to be careful with such products as they absorb heat, which will not cool down quickly in summer and radiate heat into your home. A thermal break should be installed between the paving and wall and floor systems of the building. Adequate shading should be installed over the first 4m in summer. In winter expose it as much as you like, it will provide a great source of thermal mass to heat up.