The power of energy modelling in the early design phase
There are a huge number of aspects to consider in designing a custom home. Aesthetics, personal requirements for the space, and budget are usually some of the bigger ones. Most of the thought power and focus goes into considering how a space looks, feels, and costs. One of the common errors when designing though, is to develop a beautiful, fully fledged concept that later needs re-working to achieve some energy efficiency targets or some solar-passive goals.
Focus is placed on other important aspects of a design, and sustainability falls by the wayside. For example, a house might have too much glazing on the colder side of the site, or there could be a significant thermal penetration into the building that heavily affects the stability of the internal temperature. Usually, these issues are addressed after the design is almost complete, or not at all, which means two things:
1) Things become difficult to rework without changing a whole host of other factors that have already been settled on - maybe the structural elements need to change significantly to mitigate heat loss, after already being detailed and specified. Or maybe the building footprint needs re-shaping. Something like that could be already too locked-in to be changed at all in later stages.
2) Energy efficiency gets pushed down the list of priorities - and quality of experience of the house follows, as it gets harder to heat and cool a house that doesn’t perform as well as it could. It also pushes up the running costs of the house over the long term - which, counterintuitively, plays into the budget of building a house in a way that might not be recognised initially (more on this in an upcoming blog).
To tackle this, Net Zero House often uses the energy modelling software PHPP for preliminary guidance to inform our design from the earliest stages of development, so we can tweak the important things like wall, roof and floor assemblies, floor space, window areas etc. to get the best performing house a site will allow.
PHPP data analysis
PHPP is a highly detailed simulation tool used for (but definitely not limited to) all Passivhaus certified buildings, to calculate the energy usage of a build. It takes into account the orientation on site, the type of materials & insulation in the building fabric, the climate, the amount of sunlight in a location, and other types of highly refined data, to develop a detailed picture of the way a building will function when built. Using software like this, we can crunch the numbers to clarify which aspects can be improved with the most effect. It’s also useful to trial different building materials & assemblies so we can compare costing vs effectiveness, and even embodied carbon vs carbon emissions from energy efficiency (More on this in another blog also).
While there are other necessary simulation tools that provide the energy ratings required for compliance, this method goes above & beyond to give a much more accurate picture of what’s going on. This way, we can optimise the cooperative power of house and site to produce the best outcome for its inhabitants - with the lightest footprint. Although the measurement methods are not the same for each software, rarely does a well-developed house using PHPP fall short of the compliance requirements for energy efficiency.
