Elgin Ecohome

I thought I would share some sections and reflections of a recent group assignment to design an Eco-house for a site of our own choosing. As my partner was from the Elgin area we thought we would give ourselves a bit of an extra challenge by selecting a site that sits within the flood plain of the River Lossie, combined with other design criteria which take into account climate change, resource use, a renewable energy & water strategy and the encouragement of sustainable lifestyle for its occupants. There is some cross over with regard to site analysis with my Shrubhill project (density, transport, green spaces), however we did take into a larger area when considering access to local amenities and integrated SEPA’s flood risk maps into our proposal.

 

The project gave us an opportunity to create a couple of Nicol graphs for the site. Nicol graphs show how the ‘comfort temperature’ of occupants varies with the mean outdoor temperature, particularly useful for designing free running buildings, i.e. building that do not require mechanically heated or cooling. I’m not sure exactly how this fits in with Passive house design methodology – perhaps something for further research… In essence ‘comfort temperature’ represents the fact that someone growing up in hot climate such as Saudi Arabia would feel comfortable at higher temperature than someone use to a more temperate climate such as Scotland. This is calculated by taking meteorological data for each month for outdoor maximum, minimum and mean temperatures and applying them to the following equation known as the Humphreys formula:

T_c = 0.53 (T_mean) + 13.8

Using this we created the following graphs for today and for 2050 assuming a 3 degree temperature rise due to climate change. We also combined this with the monthly solar irradiation levels to give an indication of when passive heating or cooling is required. 

Next up was an analysis of occupants and energy loads within the property – although with the scale of the coursework this was only to include electricity use. We created an imaginary family for the property and listed their daily routines, and the number and location of energy consuming equipment for every proposed room in the dwelling, from light bulbs to flat-screen TV’s. After researching energy usage amongst these appliances, we then created graphs of typical daily energy consumption for a standard summer and winter day, and using standard and energy efficient equipment. This was interesting for me, to see how much energy appliances such as a kettle use, and particularly how this is affected by the duration that certain equipment is on for. For example, running a fridge/freezer 24 hours a day, even an A+ rated one, consumes a lot of energy (not to mention the hazardous refrigerants!). Refrigerators seem to be getting larger, even though some products don’t even require cooling.  The temperature required to keep vegetables fresh varies from that required for meat and dairy. Separate compartments or employing greater stratification techniques could perhaps reduce consumption levels or unit size.

When consider the internal room layout of the dwelling, I combined the sun path diagram with the predicted time and duration of use of each room, as well as the standard requirements for connections between rooms. My final diagram is be:

By taking this approach, it’s possible to layout the rooms to match the path of the sun thus managing and maximising the use of natural daylight where possible – in this case the family uses the kitchen together at breakfast (not always the case for evening meals) so it made sense to place this room on the east facing elevation to make use of the morning sun. The flexible office space will be south facing to maximise daylight, though some shading should be provided by trees or external/internal blinds to reduce overheating and glare. The living room will be west facing to make use of the evening light for as long as possible. We constructed the inner compartment of the building (containing the stairwell) of a material with high thermal mass and with maximum exposure to the solar gain. This could be constructed out of concrete, but due to the materials high embodied energy we decided to use rammed earth, as it would be above ground. This solid mass then provides cooling by sucking in the sun’s energy during the day, and releasing it gradually when ambient temperatures drop during the day. 

All of this was work we carried out before getting to the proper renewable and energy efficiency ‘techie’ bit, which involved a water to water source heat pump making use of the nearby River Lossie and high groundwater levels, and an array of solar collectors and PV panels. Obviously location and site surroundings have an impact on the amount of passive systems you can integrate with any home, particularly with retrofit, but I find it encouraging that so many simple, low cost techniques can be employed before spending any big bucks and attaching complex equipment that requires skilled maintenance to your home.

On a final point, we attempted to overcome any flood risk by taking inspiration from some house designs constructed in New Orleans post-Katrina and elevating the building on solid structural members. This would probably have to be concrete but we have eliminated its usage throughout the building to negate its impact. Here is a quick look at the final design.