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Passive House: A Beginner's Guide

Passive House is a rigorous, voluntary house-building standard that focusses on energy efficiency and reducing the energy needed to run a comfortable home. It may seem like a relatively new concept but the first domestic examples of passive house were built in Germany in 1990 following the creation of the standard in 1988. Passive house was born not only out of a desire to build more energy efficient homes that are less expensive to run, but out of a desire to reduce the amount of energy needed to run them to minimise the ecological footprint that house-building leaves. The result of passive house building is low impact homes that save the owners money. 

Table of Contents

1. Why build a passive house?

2. What are the key concepts of passive house?

3. Does building passive house really make that much difference?

4. Top tips for building passive house

5. Examples of passive house


Why build a passive house? 

Choosing to build passive house simply means that you add more layers on to the design and build process as special considerations must be made to meet the stringent standards. You must incorporate thicker walls to accommodate a certain level of insulation, for example, and be open to the fact that large panes of glass will need to be installed south-facing to make the most out of solar heat gain. Aside from this there are no limitations to the architecture you can or can't have! There are just 5 key principles that dictate what levels of efficiency a passive house needs to hit, but there's no rulebook on how the house must look to do this. 

Young people, families and contractors are choosing to build passive houses not just because of the low environmental impact but also because of the comfort these homes afford and the money to be saved in the long term. Passive houses, when sold, can command a premium on the open market due to their low running costs, with some house builders boasting annual heating bills as low as £60. They offer Energy Efficiency Ratings in band A. Passive houses aren't just residential either with large-scale commercial buildings like offices, hospitals and schools conforming to the standard and leading the way for a greener buildscape. 


What are the key concepts of passive house? 

There are 5 key principles that underpin the entire concept of passive house. Each element must be considered thoroughly and incorporated into the build to meet passive house standards and to remain at passive house standard. These key principles are high levels of thermal insulation, passive house windows, heat recovery ventilation, airtightness, and thermal bridging-free design. 

1. Thermal insulation

Thermal insulation for passive houses must be extremely effective and so thick walls are built up using 'superinsulation' to achieve high r-values. High-grade insulation ensures that the home is well-insulated all year round which stops heat gained from the sun from leaking out. The downside to this is that this does make walls very thick. To hit passive house insulation standard in Sweden for example, walls must be at least 335mm thick with insulation to get the desired effect. Whilst this can be prohbitive on small plots, it's worth noting that only outer walls need be insulated to this level so an open-plan design can combat the loss of space from thicker walls. 

2. Passive house windows

Windows and glazing used throughout in passive houses must be quad-glazed to retain heat. Passive house takes advantage of using large sections of glass to garner heat from the sun (known as solar gain) and taking advantage of the quad-glazing to keep that retained heat in. As these types of homes become more popular the price of passive house windows has gone down and the variety of windows is greater. Large manufacturers FAKRO and VELUX for example both offer up passive house windows. 

3. Heat recovery ventilation

A mininum of 75% of the heat that would leave the home via ventilation in a passive house must be passed through a heat exchanger so that the heat is transferred to the fresh, cold air coming in. This simple heat exchange system retains the heat already in the home from solar gain and from the heat people generate which eliminates the need for a heating system. 

4. Airtightness

Airtightness is an essential part of passive house and these homes must be as airtight as possible. Heat recovery ventilation allows for air to remain comfortable and not stuffy, which is a common concern amongst passive house builders. To meet passive house standard a home must not have an air change rate of more than 0.6/hour than the total volume of the house. This prevents heat loss and shows that air isn't leaking in your home. It's often said that all the holes in your home, including keyholes, letter boxes and other small design features must not exceed the space of a squash ball. 

5. Thermal bridging-free design

Builders are able to make their passive house look however they like but an easier way to hit passive house standard is to design in a way that minimises thermal bridging. Building a house with many angles, twists, turns and corners will mean more work in the long run to get rid of any thermal bridging issues. Thermal bridging is where an area of a home has low resistance to heat transfer and therefore leaks heat more quickly than the rest of the house. The best example of this is breaks in insulation. The tiny gap between two insulation boards can leak heat out as essentially that gap isn't insulated. By building to make sure the home is as minimally exposed to heat transfer you prevent potential headaches and more work throughout. 


Does building passive house really make that much difference?

In short, yes. Whilst passive houses are to-date a little more expensive to build or to buy than the same house that doesn't meet these standards, it's far less expensive to run and they pay for that extra cost in the long run. It's said that passive houses use up to as much as 90% less heating energy than their traditional counterpart. This naturally translates to a 90% saving on heating bills which, according to Ofgem, is typically £1138 a year for a dual fuel bill. From building passive house you could be making savings of over £1000 a year in bills alone. 

There are more than just financial benefits of building passive house. You don't use fossil fuels so you reduce your environmental impact which is becoming an increasingly large factor in buying decisions in recent times. You also get an increased comfort level that many passive homeowners and occupants say is particularly hard to describe. They say that their passive house is comfortable. There's no draughts, there's no fluctuating temperatures and there's no cold bathroom tiles of a winter morning. Since the temperature throughout the house remains consistent there are no cold surfaces or glazing and there's no stuffiness thanks to the heat recovery ventilation. It could be worth visiting a passive house open day to experience this for yourself. 

The map to the right shows a selection of open days for passive houses across the UK. Find all the open days near you from the PassivHaus Trust

 


Top tips for building a passive house

As Passive House is becoming more common and a more recognizable phrase in the construction industry, architects and designers are becoming better and more efficient at building these types of homes. Consulting an architect or builder who has taken on one of these projects before could help to alleviate your worries and answer a thousand questions you may otherwise stress about.

Choose your plot carefully before you buy, especially if you’re set on Passive House. Passive Houses must be built south-facing so they can take advantage of solar gain as a main source of heat. Large windows must be installed south-facing so ensure this is possible without encroaching on your own or your neighbours privacy.


Examples of passive houses

There is no set style or form of a passive house as this small selection of examples shows.

Juri Tory architecture studio designed and built the Passive House pictured below in Austria. You can read more about the space here.

 

 

 

 

 

 

 

In Britain, Simon Conder Associates built two passive houses into the steep coastline of Porthtowan that are pictured below. Read more about the build.

 

 

 

 

 

 

 

 

 

 


For more information about building passive house and what materials we can offer to help you to build to this green standard, contact us on 01752 692 206 or use our live chat in the bottom right.  

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