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  • HPH205 : Specifying a house and creating tender documents – with Dan Higginbotham

    HPH205 : Specifying a house and creating tender documents – with Dan Higginbotham

    Architectural technologist Dan Higginbotham from Parsons + Whittley Architects talks about producing construction drawings and a scheme of works from an architect’s design.

    Interview with Dan Higginbotham

    Dan has worked with Parsons + Whittley for over 15 years, as an architectural technician and now also as a director. He has recently been working on Ben and Kay’s project and previous work includes housing developments built to Passivhaus standard.

    The architectural technologist details how the building is constructed

    Dan’s usual role is taking the architect’s 3D conceptual model and making a full set of construction drawings that someone can actually build from. These include plans, elevations and sections. As he says, “What we try to give them is a comprehensive package of information that they’re able to sit down and accurately price.”

    For a Passivhaus like Ben’s, more detail is required to ensure airtightness and avoid thermal bridges. Dan explains that there’s less risk with a house only satisfying building regs, as it would probably still pass if not sealed to such a high standard.

    Being methodical helps identify all the details

    Dan admits that things can get missed during this complex process. He tries to avoid this by following the same method each time but this is hard as he mostly works on one-off projects.

    Additional complexity comes from the many different methods of construction, and the level of sustainability clients are trying to achieve. As Dan summarises, “Although you can re-use ideas that you’ve done before, you generally have to start the whole process again depending on how people want to construct it.”

    Keeping industry knowledge current is important

    New products and resources may result in faster or more sustainable construction and better dwellings overall. Dan explains, “You’re forever learning new things, new technologies, new ways to construct things, and we just somehow have to try and keep up with that process and the industry, really.”

    Up-to-date knowledge might come from “build indexes”, forums, word of mouth, or working for a particular client. For example, a housing association might require modern construction methods or certain levels of sustainability. Dan has also found big social housing sites useful for finding out about cost-effective materials or shortages.

    Cost, simplicity, speed and specifications all affect construction decisions

    A shortage of materials could affect how you design or build things. Ben and Kay’s house will use a traditional cavity build method but this decision was threatened by a shortage of concrete blocks just before work started. Likewise, a current shortage of PIR means seeking alternative insulation materials.

    Deciding on construction materials and methods is a whole team process, with input from Dan, architect John, and practice partner Chris. It helped that Ben and Kay had already selected the finishes of the building envelope. The render finish and brick plinth suggested a cavity wall as cost-effective and simple to build, albeit with more insulation than is traditional.

    Items specified may change at a later point

    Looking at drawings for Ben’s build shows the level of detail required. The elevation showing the joinery specifies some items that they will not necessarily end up with. For example, after various discussions, an alternative supplier may provide the windows. Dan says this is quite normal: he prefers to obtain an accurate cost from a supplier rather than leave the cost as a provisional sum.

    The floor plan shows 150 mm of insulation in the cavity wall, enough for this relatively large property to get through the Passive House Planning Package. Although Dan specified high performing Knauf Earth Wool (with a thermal conductivity of 0.032 W/mK), the contractor may choose an equivalent mineral wool.

    Ecological aspirations need to be balanced with budget

    The section of the different floors shows lots of junctions that need to be considered, especially because it’s a Passivhaus. Dan tended towards methods and materials familiar to most builders rather than potentially expensive ecological features.

    Another requirement was that height be kept to that specified on the planning drawings, so Dan avoided any ecological products where more material was needed for the same performance values. He explains the choices as detailed on the section:

    • A strip foundation supports a cavity wall construction.
    • The first floor is beam and block containing PIR insulation to give a thin but solid construction with the performance needed. Above is a screed with membranes and airtightness products in between.
    • The floor and walls specify a very lightweight Aircrete block to get the best performance while minimising thermal bridging at the junction of the wall and floor.
    • The internal walls are traditional studwork or blockwork where necessary for support.
    • The second floor uses a pre-manufactured metal web floor joist (or Posi-joist) that gives a structurally sound floor with space to route the MVHR and other services without having to laboriously cut holes.
    • At the top is a fairly standard, traditional truss roof, with a more complex catslide roof to the rear. To avoid complex steelwork and associated thermal bridges and/or airtightness problems, the roofing truss suppliers came up with a truss that could form the catslide as well.

    Sections help contractors avoid thermal bridges and ensure airtightness

    Drawing more sections is useful where there are difficult details in the building, including all the junctions. Where each part of the building is different, more drawings may be required. Ben’s Passivhaus is fairly linear, but Dan was careful to show all the construction details so nothing would be missed.

    The four sections include one of the garage, one “typical” house section, one of the stairwell arrangement, and one showing the ground-to-first-floor French door, window and boarded panel arrangement.

    Developing the electrical plan is iterative

    Dan uses his experience to determine locations for electrical points, taking into account where the furniture will go. However, these positions might change later. As he says, “Each client will have their own input, particularly on light fittings and lighting locations.”

    A flexible space, for example the spare bedroom doubling as a study, can take more time to work out, as he explains to Ben, “Once we’ve actually physically got the space on site, yourself and Kay might then go, ‘No, actually I want a few more sockets here.’” This is typical of the process: educated guesses on paper are reappraised once the rooms are built.

    The team liaise with a consultant for the mechanical design

    Alan Clarke is the consultant for the mechanical systems on Ben and Kay’s project: the MVHR design, the hot and cold water supply and heating the property. Dan and the design team work with Alan on decisions like budgeting for the right boiler and the site for the MVHR.

    A major consideration is distributing the ductwork within the property. Most of the pipework is routed through the open webs of the intermediate floorspace with additional risers to the first floor. On the second floor landing a false ceiling provides a service void where ducts are routed to each room.

    The schedule of works provides more information for the contractor

    After completing the drawing package, Dan itemises every detail in the schedule of works. Reading this document alongside the construction drawings enables the contractor to produce a priced specification and to understand the methods and materials of the project.

    Find out more

    View Dan’s profile on LinkedIn

    Visit the website of Parsons + Whittley

    Transcript

    Download a transcript of the interview with Dan Higginbotham

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  • HPH172 : The impact of setting your energy target – with John Palmer from Enhabit

    HPH172 : The impact of setting your energy target – with John Palmer from Enhabit

    John Palmer from Enhabit explains what happens if you choose not to go all the way to Passivhaus standard, including how this impacts on cost, energy efficiency and comfort. He also outlines a best practice approach if you are going to build with Passivhaus principles.

    Interview with John Palmer

    John is the Managing Director of Enhabit, a company that helps to improve building performance, efficiency and comfort levels. John is a qualified Passivhaus consultant, SAP and BRE Assessor, systems engineer and experienced project manager. Prior to joining Enhabit, he ran his own low energy design consultancy.

    First understand the implications of Passivhaus for your project

    If you are trying to set an energy target, John’s advice is to start by reviewing your plans in line with Passivhaus standards. This will allow you to fully appreciate what it might take to achieve Passivhaus. Once the implications are understood, you may take the necessary steps or make a conscious decision to compromise and aim slightly lower.

    Invest in professional advice at the design stage

    John says that Passivhaus is not so much more complicated than a normal build, it just requires more thought at the beginning. One of the key thermal bridges to eliminate or mitigate is where the ground floor meets external walls, which will require careful detailing and potentially some specialist materials. Paying for some extra time with your architect or Passivhaus consultant is a worthwhile investment.

    When clients commission a design review with Enhabit, they are shown a Passivhaus model of their design and given graduated options to see what’s possible with their house and how close they can get to Passivhaus, with indicative costs for extra requirements.

    Focus on a fabric first approach, not eco technology

    John says it’s easy to get bamboozled by all the technology available. Ground source heat pumps, solar panels, boilers, etc. all have a design life of around 20-25 years and will need to be replaced. However the walls of your building will be there for 80-100 years, so the extra investment you put into them at the start will repay itself time and time again.

    Architectural aspirations may make Passivhaus harder to achieve

    John explains that in Passivhaus terms, the shape of your house is the ratio of your liveable area to outside heat loss area. So you may need to compromise on an ambitious design if you want to target Passivhaus.

    If your plans have already incorporated professional advice, and you intend to follow a very high-performing fabric first approach, it may be you just need to add in a MVHR (mechanical ventilation with heat recovery) system.

    Alternatively you may find you haven’t gone far enough with the fabric of the building and need to change the specification of insulation, glazing, etc. This is typical of retrofits, where John says it’s quite hard to achieve the levels required for Passivhaus with the existing fabric.

    Heating a Passivhaus costs a very small amount

    The annual space heating demand in a Passivhaus should be no more than 15 kilowatt hours per metre squared per year. John comments that this is a very specific number and you may decide this is unachievable.

    The key is to understand what number you can get down to, and what that means. For example, a target of 30 kWh will cost you twice as much to heat your property in any given year than it would have done if it were a Passivhaus. But heating a Passivhaus costs very little, so doubling very little isn’t that much and is likely to be better than other new build properties in the UK.

    Every design decision will impact on comfort levels

    Doubling your space heating demand to 30 kWh will impact on comfort but the nature of this impact will depend on why you haven’t achieved the Passivhaus target of 15 kWh. John gives a few examples:

    IssueImplicationsImpact On Comfort
    Insufficient insulation in wallsHeat loss from wallsFeeling cold off the walls
    Poor detailing where walls meet ground floorThermal bridgingIf bad, noticeable cold spots and possible condensation/mould
    Window specification isn’t triple/ high-quality double glazingCold will radiate off the glazingFeeling cold in rooms at certain times of year

    Thermal comfort is all about constant temperatures

    Many homes, especially Victorian buildings, tend to have rooms that are hot near the ceilings but cold at lower levels due to drafts and a lack of insulation below the ground floor. John explains that although the average air temperature in the room might be ok, having cold feet and a hot head will feel uncomfortable! Paying attention to thermal bridges and insulation will help to achieve what John calls good temperature stratification.

    Building regulations rely on people opening windows for required ventilation

    Although our awareness of temperature is quite good, it’s harder to detect poor air quality. We may notice smells and detect when rooms are a bit stuffy, but that’s about it.

    Humidity, VOCs (volatile organic compounds), odours and nitrogen oxide levels are all examples of pollutants within buildings. John advises we need about 30 cubic metres of fresh air per person per hour moving through a property to deal with pollutants, but this isn’t achievable with trickle vents and extractor fans unless you start opening windows.

    An MVHR system will deliver the required level of ventilation, but there are other mechanisms out there superior to extractor fans that will give extra ventilation but perhaps not cost as much.

    Insulation, glazing and ventilation will cost more, but not much more

    These three aspects are typically more expensive than a normal new build, as a Passivhaus requires:

    • More insulation – but you’ll only be paying more for materials (approx. 0.5% increase on overall cost); the labour costs are the same
    • Triple glazing, for thermal performance and to avoid condensation and mould – the gap is closing between triple and double glazing prices
    • An MVHR system – for an average sized house this may cost £9-10k for supply and installation

    Of these, the greatest return on investment will be insulation.

    Some builders are willing to learn

    Hiring the right people to build a Passivhaus is another factor to consider. Although it’s still relatively new to the UK, John has found that builders relish the challenge of doing something that requires more detail and thought; they appreciate the ability to measure how well they’ve done, and revel in achieving the standard. He adds, “You have big, hairy builders hugging each other on site when they get their final air test and they’ve got down to the right levels.”

    Five helpful tips from John

    1) Visit a Passivhaus or speak to someone who lives in one, to see what it can deliver from a living experience

    2) Find out what would be involved in achieving Passivhaus for your project

    3) Understand how each decision affects the final design, floor space, efficiency and comfort

    4) Put an MVHR system in, regardless of your airtightness target; ventilation and air quality are worth doing as standalone

    5) Have some form of quality control in place, even if you’re not targeting Passivhaus, to get the results you’re expecting

    Find out more

    Passivhaus Trust

     

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  • HPH121 : The pros and cons of building a Passivhaus with a kit or system – with Janet Cotterell from Passivhaus Homes

    HPH121 : The pros and cons of building a Passivhaus with a kit or system – with Janet Cotterell from Passivhaus Homes

    Author and architect Janet Cotterell talks us through the different ways of building a Passivhaus using kit and system methods.

    Janet Cotterell

    Interview with Janet Cotterell

    Together with her co-author of The Passivhaus Handbook, Adam Dadeby, and their team, architect Janet Cotterell has been developing the PH15 system for building Passivhaus homes.

    Janet became interested in sustainable architecture after completing a Masters degree during a break from her work. She felt her responsibility as an architect was to get the fabric of the building right by making it as energy efficient as possible and it was around this time that Passivhaus was just beginning to emerge. Rather than trying to invent her own solution, she was happy that Passivhaus appeared to work and was impressed that it had been invented by a physicist.

    Efficiency in time and efficiency in quality

    Building a house with a kit isn’t particularly common in the UK but is used much more widely in Europe, North America and Canada where the self build market is far more buoyant.

    Janet explains that the key benefits of building this way are that precision construction takes place off site and in good conditions. Once on site it goes up quickly and saves on overheads.

    Akerman Frame
    Akerman Frame

    ‘Systems’ retain the enjoyment of construction for a self builder

    Janet would describe a ‘kit’ as being pre-made, complete components which almost click together, with a Huf Haus being the example recognisable by most people. A kit may be panels which have windows and insulation pre-installed, be airtight taped (in the case of an energy efficient home) and arrive with the wiring in place. The pieces are going to be large, heavy to transport and put in position, with far less being done on site.

    A system tends to be a set of components that are brought together on site. While the frame is pre-cut, they aren’t made into panels and don’t have windows pre-installed.

    PH15 Frame - aerial on 25.2.16

    PH15 KIT FRAME

    Passivhaus Homes’ PH15 system is designed to be simple on site while still retaining some of the elements of skill that people who are self building often tend to enjoy. No specialist equipment or tools are required, though people do have to be more careful and precise than on a typical UK building site, but as Janet says:

    “If you want to be energy efficient you’re going to have to be a bit more precise! But you can make everything else as easy as possible.”

    A Passivhaus kit or system can save time, complexity and money

    One advantage of using a kit or system for a Passivhaus self build, is that there can be unusual details, like the airtightness details between the walls and floors, or walls and roof, or around the windows. Having these pre-solved in a kit or system can be a huge advantage in terms of time and money saved in trying to work them out for yourself.

    Some of the Passivhaus materials and methods can be unfamiliar to the UK market. A system approach therefore takes away any uncertainty around what’s needed, and can make it easier to estimate the price. Janet feels that a lot of tenders are elevated because people are unfamiliar with things like the windows, the ventilation system, the tapes and membranes. For somebody who hasn’t done low energy building before, this method frees up their time to concentrate on just putting it together on site with the benefit of cost certainty, which is particularly useful if building to a tight budget.

    The PH15 system

    The PH15 system has been designed to be flexible, though the more complex the form, the greater the costs will be.

    The system minimises thermal bridging by using a standard sized I-joist frame made from waste timber. They avoid using steel inside the house, and have wood fibre boards on the outside and use laminated veneered lumber. The timber based floor joists mean that the services and ventilation system can be fed through. The system includes a guaranteed airtight board which has all the tapes and membranes, as well as triple glazed doors and windows and the whole ventilation system.

    There are two methods of cladding the timber frame: lime render, which can be to different finishes and colours, or timber weather boarding which can be done in a myriad of ways to create different aesthetics.

    To start with they had just one or two house designs and they had pitched roofs. Now, their designs have developed including with living roof systems, and Janet sees lots of potential for being creative with ever more interesting designs and options.

    Torquay visualisation
    Torquay visualisation

    Passivhaus Homes have designed the system so that somebody with carpentry skills can build it themselves, with just some additional training material and sessions. For example, there’s a day’s training that goes with the frame. Janet stresses they’re not trying to teach people how to build Passivhaus or low energy homes in general, but are just teaching how to put together this Passivhaus home. They also provide technical support by phone.

    Janet recommends early planning to the kit, rather than sending in planning drawings and then trying to make the kit work:

    “And we can provide basic information about the kit which tells you this is the size of wall you need to allow, just a basic sort of design guide, so that when you’ve finished the design you know that that is actually going to suit the kit and it’s going to work without any extra problems.”

    Costs could be worked out, with a small margin of error, from a set of planning drawings, however Janet recommends that for an accurate price they would need a set of frame drawings and a proper MVHR (Mechanical Ventilation Heat Recovery) design.

    Brick and timber frame aren’t a perfect match

    In the UK we have a tradition of using brick construction, and this can be a finish that people will want to incorporate into their design. Choosing a brick finish for aesthetics on a timber frame building can be challenging. One of Passivhaus Homes current projects uses a brick slip system. Janet says you can do a full brick skin but the brick is being used purely as a rain screen or as an aesthetic to respond to UK tastes. Her own feeling is that you can instead introduce brick accents to a timber system and address it, rather than doing whole brick.

    There should be more Passivhaus kit / systems available

    Janet feels that there should be many more people self building and custom building in the UK and that there needs to be a lot more land released to enable that. She also sees no reason why all this new housing shouldn’t be built to Passivhaus standard.

    Janet believes there needs to be more of these types of Passivhaus kits and systems on the market. Passivhaus Homes completed the second retrofit to full Passivhaus in the UK, and a man who worked on the UK’s first retrofit to full Passivhaus standard has also been developing a kit/system approach, although Janet’s understanding is theirs is a more panel based approach.

    Janet also mentions Architype who in their ArchiHaus scheme are building a factory to construct the pre-made panels for the development of 150 houses.

    BerryDownPHH-DesignHouse

    Find out more

    Visit the website of Passivhaus Homes

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    Transcript

    Download a transcript of the interview with Janet Cotterell.

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  • HPH004 : The Passivhaus Standard #2 with Dr Wolfgang Feist (Passive House)

    HPH004 : The Passivhaus Standard #2 with Dr Wolfgang Feist (Passive House)

    Dr Wolfgang Feist describes how better energy efficiency opens a path to making us less dependent on fossil fuels and we have that knowledge now.

    wolfgang feist

     

    Interview with Dr Wolfgang Feist

    Dr Feist explains that his early research in the 1970s was addressing how to deliver the growing demand for energy in the world. When examining what the energy was used for, the surprising result was that most of it was wasted. So improving energy efficiency was the clear route forward. If you consider the services you need then you can design a building in a way that it uses far less energy. Scientifically speaking this is quite easy to do; the bigger challenge is getting that through to the market.

     

    The Passivhaus Standard is Very High Energy Efficiency

    By improving the building’s envelope you reduce the energy losses you normally have, so that you only need a very low amount of heat to keep it warm or cooling to keep it cool. This is in the range of a tenth of what we used to need in the past. It not only reduces the amount of energy you need but it also improves the comfort in the building, too. With a far higher quality of building envelope, another benefit is that it lasts longer. And, as it’s simpler, it becomes easier to maintain.

     

    Passivhaus Principles Can Be Widely Used

    Dr Feist explains that a building that meets the Passivhaus standard can be of any style and for an purpose (offices, swimming halls, schools and dwellings etc.). It also lends itself to any kind of material: masonry, timber construction, load bearing structures with concrete, whatever you want.

     

    Old Habits Die Hard in The Construction Industry

    As a very conservative industry, the construction industry tends to do what they have always done and that means it’s not easy. However, change is becoming more rapid. The key is that they must decide they want to learn this new way of doing things.

     

    Energy Will Only Get More Expensive

    Our energy problems are not in the future, they are happening right now. Over the last ten years the cost of energy has risen significantly and that is set to continue – fuel poverty already exists. Also, the consequences of using fossil fuels on such a large scale mean that we have a growing amount of Carbon Dioxide (CO2) in the earth’s atmosphere. We need to change the way we use energy. Using less energy will in turn burn less fossil fuel and thus reduce CO2 emissions. Currently, around the world, over 80% of our energy still comes from fossil fuels.

     

    The Passivhaus Standard is a World Standard

    Dr Feist says that the Passivhaus standard is a world standard, but it is a method of doing things. Therefore what works in one country cannot necessarily be transposed to another. It’s a method of how to design a building compatible to the climate in which you reside.

     

    Passive House Principles

    In the UK’s situation, insulation is the most important factor. It must be in such a way that it avoids thermal bridging. Then the building must be airtight, which is something they have not been in the past. Improved windows have a very high influence on the energy balance of building, too. Due to the airtightness, a ventilation system is also necessary.  So the four factors are insulation, airtightness, good windows and ventilation.

     

    Passivhaus Standard Certification

    It is well documented what a building is that meets the Passivhaus standard. That’s why certification allows you to know that the building meets the criteria. In the UK the Passivhaus Trust has a list of certifiers. If you come to sell a house, this certification becomes a quality and performance guarantee.

     

    A Future Worth Living

    Through his research at the Passivhaus Institute Dr Feist is creating better components, such as more efficient windows. He’s motivated by seeing new projects realised. Recently he has been working with the city of Frankfurt to build the world’s first Passivhaus hospital. The government and European Commission are seeing the huge benefits and encouraging this advance. Dr Feist also helps organisations around the world to gain members and knowledge.

     

    How World Governments Can Play Their Part in Driving Forward Energy Efficiency

    The most important stride could be made by governments creating an environment where innovation is accepted. Incentives can also play a part and they don’t have to involve money. Dr Feist details an example in Italy where truly energy efficient house builders are allowed to build on a bigger proportion of the land they own. That way it doesn’t cost the taxpayer any money, but it does provide investors with an incentive to build energy efficient homes. Governments can also circulate literature about how to improve efficiency in new construction and in refurbishment of existing buildings.

     

    Timing is Everything When Retrofitting Existing Housing

    The best time to improve the energy efficiency of a house is when something needs to be done anyway. As our existing housing is not static, but in a cycle, there will come a time when repairs etc. are necessary. This is the time to improve energy efficiency… when the scaffolding would be going up anyway. Dr Feist stresses the importance of going for the best products, too. This is because the job may not be done again for many years.

     

    A Path Away From Fossil Fuels

    Based on the physics there is no need to use energy to create comfortable temperatures in buildings. Energy savings could be reduced further, not to zero but to almost zero. However, there is a certain amount of renewable energy available and with the advances of Passivhaus they reduce energy consumption to 1/10 of what it has been in the past. Therefore the required energy is low enough that it will be available from regional sources anywhere in the world without a big problem. So in the end there is no need to go much further than that but of course it could happen.

     

    Transcript

    Download a transcript of the interview with Dr Wolfgang Feist.

     

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