5 Key Lessons from Passive House
How do you build a house that’s cool in the summer and warm in the winter? One way is to design it to Passive House standards.
New to Passive House? Take a look at the Passive House Institute for a detailed introduction.
If you're in a rush, think of Passive House (or Passivhaus) as a method for constructing highly energy-efficient buildings. Typically, a Passive House can achieve energy savings of up to 90% compared with existing buildings and over 75% compared with the average new build.
Not bad when you consider the current crises of rising energy prices and the apparent impacts of climate change.
People often praise Passive Houses for their high levels of comfort and efficiency. They tend to have lots of insulation, high-quality air-tight windows, and a carefully planned ventilation system that together make pleasant living environments. Their design provides comfort all year round-warm enough in winter and comfortably cool in summer.
But, and there's always a but, the challenge with designing to Passive House standards is the cost.
Building a property that meets the rigorous Passive House standard can cost hundreds, if not thousands, of pounds extra per square metre. On a typical 100m2 family home, you could be looking at an extra £100k in costs.
So, what can you learn from the Passive House design standard and apply to a project with a more modest budget? How do we make a more efficient building that's cool in the summer and warm in the winter without breaking the bank?
Here are five key areas from he Passivhaus standard to look at:
1. Insulation
Perhaps the quickest win when designing highly efficient buildings is to go above and beyond the minimum requirements for insulation.
This insulation could be in the loft or the walls, including internal and external insulation. It's easy to understand how this helps keep a home warm in the winter, but what about summer? Wouldn't it also have the same effect of keeping it warm in the summer? Actually, no.
According to the International Passive House Association:
“Insulation does not create any additional heat; it only reduces the heat exchange between systems with different temperatures. Therefore, it also protects a cool system from gaining heat from the surroundings. This is where the common example comparing a Passive House building to a thermos flask comes in handy – it works just as well for a cold liquid as for a warm one.”
Step 1 is to ensure you specify plenty of insulation in your new building.
2. Windows & Shading
Large expanses of glass have become a feature of modern architectural design. However, sadly, they are not that efficient at controlling temperature. There's a reason why greenhouses are mostly glass.
However, you can’t have a building without windows. We need windows to provide lots of natural light, to see outside, to let fresh air in and to benefit from solar gains during winter. I don’t imagine living in a windowless home will be that comfortable.
The challenge is to get the balance right between natural light and thermal management.
We do this through appropriately sized windows and the use of shading systems. In a Passive House, shading plays an essential role in keeping a building cool. Simple options include good curtains and blinds on the inside of a window. Externally you could think about shutters, often used in warmer countries, or structural systems such as a brise soleil.
These will all act to keep out the sun’s warmth during the summer months without preventing solar gain in the winter.
Don't forget about the quality of the window system too. There are many options for glazing, such as triple glazing, that will help manage thermal gains and losses through the glass itself.
It’s essential to consider the impact of the new building regulations when it comes to the amount of glazing in your property and the impact on uValues.
3. Ventilation and Airtightness
Passive House buildings are generally equipped with a mechanical heat and ventilation system to keep a constant supply of fresh air running through the building.
A client of ours installed a mechanical ventilation system and swears by its impact on air quality in his home. However, they can be expensive, so what are the less costly alternatives?
Perhaps the quickest win is to ensure the building is highly airtight and therefore prevent cold or warm air exchanges. You want to keep warm air out in the summer and in during the winter months. And, you guessed it, cool air in during the summer and out during the winter.
This is where air tightness is essential. Buildings leak air around the windows or in the building's joints, so the technical specification and build quality are critical.
4. Orientation
A building's orientation can be more challenging to manage; often, a building's orientation is limited by the site, especially on works to an existing building. However, it is essential to consider what direction the building is facing and where the windows will go.
Windows facing east or west are at particular risk of solar gain because the sun's angle makes shading difficult. South-facing windows are more easily shaded during the summer whilst still taking advantage of most of the solar gains from the sun's lower angle during winter.
Here's an example of how we would plan out the orientation at the early stages of a project to consider the sun's path throughout the year:
5. Indoor Sources of Heat
It is also essential to be aware of indoor sources of heat, for example, cooking, electrical devices, hot/cold water systems, central heating and technology.
The output of all these indoor heat sources can uplift the overall temperature within the building. Passive Houses minimise the energy consumption of all services and encourage the use of efficient equipment throughout a building.
Finding efficient heating systems and other building services is no more challenging than for devices such as computers, televisions etc. Just make sure you specify the most efficient systems and appliances.
They will all cost more upfront, but the running costs should, over time, make up for the extra costs.
So there you have it, five factors we can learn from Passive House that will help to make our homes and buildings more efficient, keeping them cool in the summer and warm in the winter and lowering our running costs.
You can find out more by speaking with our architectural team. You can find our contact details here.