Low energy house O
Published July 16th 2009. Updated 16th January 2011.
The concept: Is a flat pack style home. A 3mx3m modular layout, designed so the occupant can decide their own floor plan from 18m2 up to what ever m2 in a flat pack kit. Quantities for the chosen house type would be arranged and supplied from the warehouse and delivered in a simple kit, erected quickly and made water tight in a week ready for the chosen fixtures and fittings to complete the build.
I have currently produced two floor plans just as an example of what’s possible with the design. The illustrated project below is the first to come off the drawing board. The second was developed specifically for a narrow piece of land and on a tight budget. Due to strict planning restrictions with the low energy house at Martinsberg we were not free to run away with the design. It had to have a red-pitched roof, blend in with the surrounding, no more than 20% solar panels to the roof and restricted to a 50m2 floor plan. The new plans move away from the traditional three bedroom house style and offers the public an alternative “house” with minimal yearly running costs. I can only vouch for the the houses proposed performance figures here in Tubingen where summers reach +30 and winters can dip to -20, so not the easiest of climate conditions to design for.
The Architecture: Simple and Minimal
The design is made-up of three squares encasing one another growing in size by the golden ratio.
The outer shell provides the shade and protects the main house from the harsh elements by means of 5m high rolling vertical Larch shutters that can be fully opened and closed to suit the changing seasons. The middle Square is the living accommodation spread over two floors, the inner square creates a protective calm and quiet courtyard helping to stabilize temperatures to the middle square and offering a semi-exposed area from the elements.
The floor plan you will notice is nothing new. It’s a floor plan that has been used time and time again through history. I don’t particularly “do” standard internal walls and doors so the centre courtyard design naturally gave me that room-dividing feel I wanted without using traditional methods, but really the main reason for the courtyard is a ventilating advantage to the design. It not only helps the external winds to be easily pulled across the whole internal space but it also provides a cooling oasis in the summer for the building to be able to breath and for the occupants to be able to retire somewhere constantly cool. In the winter the house is designed so the low-lying sun can penetrate directly through the inner courtyard and providing an encased sheltered sunny winter garden behind glass.
It’s still on the drawing board. Well it is nearly finished; just don’t want to up load it. One major change I have done from what appeared in the Martinsberg project is to ditch the submersible log burning wooden hot tub for a more minimal Ofuro Japanese bath on the west terrace. Working on the details now of getting hot water from the solar tank to supply the Ofuro and external shower but its all just technical details to work out. Just need to transfer the garden-planting scheme over onto the computer as it’s all still in hand drawings.
With the aid of the model I tested a wide array of potential ideas. As shown on the next pages the 170m2 version was designed to be around a centrepiece silver birch courtyard, not just for design purposes but an important role in the concepts passive design. The model was more useful than just visually seeing the project in a three dimensional proposal. It helped pick out concept errors, the movement of natural light around the building, general internal aesthetics, scales and proportions with the golden ratio, modular timber sizing, flat pack research and material quantities.
As shown in the photos I firstly prepared a cut list for the modular framework so I could assess material lengths and estimate transport quantities.
I use http://www.gaisma.com for sun plotting data. The model will represent these figures in real life showing the extent of the suns ability to penetrate deep into the concept during the winter months as well as displaying true shadow lines achieved so can we estimate the extent of the concepts summer shutter design.
The next step on from living in a low energy house was to collect the18 months of recorded data and see what we could do to improve the performance figures. Better figures can easily be reached but at what extra cost. Unlike the first project the Orient Chapple is designed to be located on a flatter plot. Land price will increase but access, excavation, engineering, foundation design and split level wall construction costs will drop in price.
New topics I’m currently researching for the project include: Solar chimney, cooling centre stack, earth ramming, earth tubing, green roofs, solar tanks to tank-less water heater systems and under floor heating.
The tried and tested products already used on the low energy house will obviously be incorporated into the proposed technical brief.
Extensive (Sedum Carpet) Green Roof.
Due to the immense temperature gains with flat roofs we increased the existing 14cm high performing insulation by 2cm to help stabilise thermal time lapsing. We would split the roof design between a green roof style over the main house and sheet metal cladding to the concepts over hangs. This would reduce problems of over heating in summer to the main roof and still having a large enough surface area of roof to collect non-contaminated rainwater for the concepts rainwater harvesting storage requirements.
Passive south elevation
As the low energy house, Martinsberg had restrictions to the floor plan size it was not feasible to create a second layer glass wall. For this project Tri- fold doors will be located to create that needed summer heat / winter sink buffer passive design requires. It means the new house will take full use of passive design. This in return will account for the biggest saving for artificial heating/cooling to the concept idea.
Push the roof and walls by 2cm with high performance insulation. I’m going to push up the North elevations insulation internally by 8cm mineral batt style to improve the acoustic value and to in-case the projects pipe work.
Suspended ground floor
Increasing the floors thermal mass by means of high performing insulation rather than standard stone wool between the joists and also upping the load-bearing insulation above the joist.
The heating system
I’ve been working out on what it seems like forever to configure the most cost effective way to heat and supply the new house plan.
So here’s the proposed system.
The same log burner will be incorporated into the design offering a centerpiece fireplace to the room while contributing its hot water along to the 900ltr solar tank. Increasing the hot-water solar system to accommodate 6 adults so will increase the roofs solar heating panels up to 12m2, but how to heat the rest of the house? Under floor heating (wet system) supplied from the solar tank to three ground floor zones. Will work the same frame structure idea so the warm air is not trapped under the first floor but allows the heat flow up and through the building so no UFH to the first floor. My problem was, what happens if the system is over loaded in the winter and takes all the heat generated in the tank and starving the domestic hot water supply. A few years ago I researched into tank-less hot water systems that use a tiny amount of electric to heat water. As you know all the energy in heating water is from 0 – 9 Degrees. Heating water up from this figure uses very little electric. The proposed system will run its domestic hot water requirement firstly through the solar tank then run through the tank-less water heater achieving a constant supply of hot water. This means it will always have a chance to be pre-heated before going through the tank-less system. This will take the pressure of the solar tank leaving the bulk of the hot water for the under floor heating.
The final stage will be to add a 1.8kw Photovoltaic solar system on the green roof so to balance out the energy demands in winter, electric back to grid method. It would mean the energy used through the winter would balance out from the electric generated in the summer for the tank-less hot water running cost.
The photovoltaic system should equal out the electric demands used per annum but further research needs to be assessed to achieve realistic figures.