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What questions should I ask when buying an eco/green/low energy home?

Posted by on May 9, 2019 in Pete's Blog | Comments Off on What questions should I ask when buying an eco/green/low energy home?

From many years of painful conversations with people who have “bought a pup” I bring you this simple list which I hope will empower you to get what you think you are getting. I have to declare my bias: I moved to Passivhaus after many years designing the thermal envelope and building services for low energy buildings. In the early years there was a great deal of “greenwash” and we came up with some simple ways round it, but were wowed by the Passivhaus standard and the detail that went into the calculations, and more importantly, the monitored evidence. So don’t be surprised if I’m pushing Passivhaus as the complete package – I know it works. That said, there are other people working away to give you a comfortable home without costing the earth. But there are still some people who, how shall we say, aren’t quite on the ball as regards the energy performance of their offering. How do you tell who is OK? Simple, 3 questions: 1. Has it got a Mechanical Ventilation System with heat recovery (MVHR)? Any low energy home will have this, so if it hasn’t, walk away. There are some other ways of dealing with good ventilation with low energy use, but I haven’t yet seen anything that is as robust as MVHR units. a. Does the system use flexible or plastic rectangular ductwork? Walk –they leak like sieves. Spiral wound or semi rigid ductwork is OK b. Can you see the Design and Commissioning documents? We have seen so many badly designed MVHR units I want to scream. Commissioning documents show the air flow through each terminal, as set up, and form the basis of performance. No documents, walk! 2. What is the airtightness of the building. If it hasn’t been tested, walk away, as they obviously haven’t got it. Current building regulations have many get-outs so contractors can declare that they “tested one the same 3 years ago”. If you do have a test result you can grade it as follows: a. Over 10 m3/m2/h at 50 Pa test pressure – impossible as this is the Bregs limit if its tested, so if it is over 10, someone will have pretended to have never tested it and they will have moved onto another house/flat on the same site. b. Between 10 and 5 m3/m2/h @50 test pressure. About the mean for UK new Housing. Walk. c. Between 5 and 3 m3/m2/h. Bad but better than the average. d. Between 3 and 1 m3/m2/h. Not bad. Could do better. e. Below 1 m3/m2/h, hey, near Passivhaus territory. Congratulations! 3. Well if they have done the above, they have cracked Passivhaus, so they might as well get it certified- have they? Beware of contractors claiming “Passivhaus principles” which might be fine, but without the evidence in the first two questions I wouldn’t go near them, life is too short. If it is a certified Passivhaus, it will answer all the above. (just to be clear, I am a certifier) Notice I haven’t even looked at insulation yet, the above are usually all that is needed. Good luck. Below a simple pictorial of the above points.   Buying an Eco-House? (128.7 KiB, 747...

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Airtightness, Airtightness, Airtightness

Posted by on Mar 18, 2019 in Pete's Blog | Comments Off on Airtightness, Airtightness, Airtightness

What makes a building low energy? As most readers know, Passivhaus is one of the leading ways to realistically reduce the need for heating or cooling energy in buildings, both new build and retrofit.  I say “one of the” but I don’t personally know of any other that works. Minergie in Switzerland is OK but it’s really a Passivhaus copy. So what are the fundamental propositions of Passivhaus?  I would say there are three: The building must be airtight.  Wow – living in a plastic bag! How horrible!  Well actually its quite comfortable. No draughts, constant temperature, maybe a bit weirdly uniform. In fact, after the initial exposure, most people don’t even notice the environment internally, which is a definite success!  After all, thermal comfort = lack of thermal stress.  But how can we ensure that the air is fresh and smells and excess humidity are removed? This is the second point: The building must have a controlled ventilation system to ensure indoor air quality is maintained at all times.  So far, the only systems we have used are mechanical, since all the natural ventilation systems we have found are unable to provide a consistent ventilation rate,  instead vary dramatically with the weather.  People generally will open windows only when the internal air quality conditions are quite bad. And the third is insulation.  Lost of insulation, all joined up to itself like a good polar suit all round, no leaks anywhere. And that’s where airtightness comes in again.  If air can leak through to the other side of our insulation, then its not doing anything. Bob Lowe reported this as “convective bypass”, but it’s basically crummy workmanship (or to be kind, installation without any understanding.) So why have I titled this Airtightness, Airtightness, Airtightness? Well if we look at the three options above, they all end up requiring airtightness to make sense. The heat recovery aspect of ventilation is a waste of time if you home has a leakage of much above 3 achr at 50Pa. And if the insulation has air washing around both sides due to a lack of airtightness, its not going to do anything.   So:  low energy building = airtightness...

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What Kit do I need to commission MVHR systems?

Posted by on Feb 26, 2019 in Pete's Blog | Comments Off on What Kit do I need to commission MVHR systems?

We get asked this frequently, and the answer depends a lot on how much work you expect to do and what level.  You need a capture hood to get any sort of accuracy at all, but there are three main types:: The basic  is the Testo or Airflow anemometers, Testo better built.  What you have to recognize with these hoods is that they are seriously affected by turbulence, so if you put them on a supply terminal designed to give a jet your readings will be seriously out – BSRIA have done a report on this. Extract ok.  The other main issue with them is that they cannot measure much above 60 m3/h (~20 l/sec), which means they cannot be used for measuring total flows on outside terminals, which in turn means you cannot check for duct leakage (sum of internal flows should equal the external flow).  This limit is simply due to the small size of the vane: 100mm diameter, which at higher flows puts an extra resistance on the mvhr system and so gives daft readings.  Cost a  few hundred £ depending on how many hoods. Very light ( 1kg?) The next step up is the large area hot wire anemometers with a much larger throat (200mm sq) so can measure larger volumes and doesn’t seem to have the turbulence issues above.  £2k? Swemma main brand. Fairly light ( 2 kg?) And finally we have the balometers, which have a powered fan which runs to balance the pressure inside the measuring chamber to outside, so there is little change on the whole system balance.  Most accurate but a little heavier (3kg?) and cost (£3k?). Which you get depends on what you are doing.  The anemometers are fine but only if the system has no leaks (tricky to know) and you can’t really do a Passivhaus without a separate duct leakage test. The hot wire are fairly light and accurate, and for all day use are the best choice. If you get mostly called out for fault finding, as we are, then the balometer is best for accuracy, so we put up with the extra weight. Remember that you will have to calibrate the unit once a year, which costs a couple of hundred quid.  It worth also thinking about hiring: BSRIA has reasonable rates, and each unit is calibrated before it is sent out.   Its also a good way to find out what each unit is like to use. postscript: It has been pointed out that the CIBSE commissioning code says the only absolute measurement recognized is a pitot tube, with measurements taken at intervals across the duct.  This is fine for commercial pipe ducts, but hopeless for residential, where the small ducts and lack of straight runs before and after measurement points  means that it is wholly impractical. Don’t try...

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WARM Take Home CIBSE Awards!

Posted by on Feb 13, 2019 in news | Comments Off on WARM Take Home CIBSE Awards!

WARM won two awards at last night’s CIBSE Building Performance Awards! Sally and Caroline represented us. We were all chuffed, in particular with the Building Performance Consultancy award, as our practice numbers only 7 employees! Winner Building Performance Consultancy (up to 100 employees) Highly Commended Project of the Year – Residential Project: Cameron Close We’d like to thank the rest of the team involved on the Cameron Close project, notably: Building owner: Southern Housing Group Architect: PCKO Architects Mechanical/Electrical Engineering: Clarkes Mechanical Main Contractor: Stoneham...

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Goldsmith Street Passivhaus under construction

Posted by on May 4, 2018 in news | Comments Off on Goldsmith Street Passivhaus under construction

Goldsmith Street Passivhaus under construction

  The Goldsmith Street Passivhuas project commissioned by Norwich City Council and being constructed by RG Carter is well underway on site. The Passivhaus development is progressing quickly, it will consist of 105 dwellings, a mix of 2- and 3-storey houses and apartment blocks. WARM role has been the mechanical service design and Passivhaus consultancy. We have developed simple services with the focus on designing for install, commissioning and use. Also, as Passivhaus consultants our input has been most notable on the glazing design, where we have helped balance heat loss, overheating risk and daylight design. Follow this link to see a drone footage of Goldsmith Street Passivhaus under construction: https://vimeo.com/262950617  ...

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Intake Location Calculation

Posted by on Jun 20, 2017 in news | Comments Off on Intake Location Calculation

Intake Location Calculation

On many projects we need to decide how close we can locate an air intake to a polluting exhaust or boiler flue. This workbook is for calculating the minimum recommended distances between intake and exhaust openings and boiler flues using the equation provided in ‘Annex A of BS EN 13779 Ventilation for non-residential buildings-Performance requirements for ventilation and room-conditioning systems’. Note that this calculation does not take into account directional louvres. Click to download: Intake Location Calculation Workbook...

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PHPP WARM Results Sheet v6.06 Released

Posted by on Nov 25, 2016 in news | Comments Off on PHPP WARM Results Sheet v6.06 Released

PHPP WARM Results Sheet v6.06 Released

Dear all, Version 6.06 of our results sheet has just been released – now with added goodness! Click to download:   PHPP WARM Results Sheet v6.07 (204.2 KiB, 5,318 hits) The biggest update is a button that automates the process of recording the current PHPP results in the “revision history” table. The sheet is also now compatible with PHPP 9.6. Important note: the button uses a macro to do its magic. Therefore, it will only work if the PHPP you are using is saved as a macro-enabled spreadsheet (.xlsm). However, you can still use the results sheet in a PHPP saved as .xlsx, it’s just that the button won’t do anything and you will have to copy and paste results manually. Full instructions on how to insert the sheet into your PHPP, and how to use it, are in the sheet itself. Compatible with all versions of PHPP 8 and 9, up to PHPP...

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The Truth is Out There (Window Specifications)

Posted by on Aug 15, 2016 in Guides | Comments Off on The Truth is Out There (Window Specifications)

The Truth is Out There (Window Specifications)

(Post by Karl and Liam)   Glazing Frame Evidence Required for Passivhaus (140.8 KiB, 2,494 hits)   Glazing Frame Specifications for Passivhaus (87.0 KiB, 2,205 hits) In a darkened basement there is a series of files, full of mystery and unanswered questions. The investigations held within these files are frequently hampered by a wall of secrecy which surrounds the subject matter. At every turn there seem to be half-truths and prevarication, with questions being sidestepped or overlooked. However, the investigators aren’t looking for proof of alien abductions, a vast conspiracy in the military-industrial complex or even the cause of some strange events in backwoods Virginia, likely caused by a limited gene pool and a chemical waste leak. They just want to know the U-values for some window frames and glazing. We’ve lost count of the number of times we’ve asked for this information. We know it’s out there because it’s essential for BFRC certification, apart from anything else, but most manufacturers really struggle to provide it. When asked which window manufacturers to approach, it’s so much easier to suggest ones who are able to give us this essential data without the hassle of an email trail as long as Hilary Clinton’s list of deleted messages, or a series of phone calls long enough to send an FBI phone-tapper into a stupor. This is far from ideal: we would prefer, as both Designers and Certifiers, to be able to identify the best windows for any given project based on their technical performance. So, for the benefit of window suppliers and manufacturers, we’ve developed an Excel sheet and PDF, which tell you exactly what we need to know and to what standard the numbers should have been calculated to. Please make the evidence and filled-out spreadsheet easily accessible and downloadable from your website, and you’ll earn the gratitude of legions of Passivhaus designers beavering away at their projects. They’ll probably want to specify your windows, too. The truth is out there – please help us to find out what it is. PDF (read this and upload thermal reports to your website):   Glazing Frame Evidence Required for Passivhaus (140.8 KiB, 2,494 hits) Excel sheet (fill this out and upload to your website):   Glazing Frame Specifications for Passivhaus (87.0 KiB, 2,205...

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Free advice! show us your designs and we’ll improve the energy performance

Posted by on Jun 27, 2016 in news | Comments Off on Free advice! show us your designs and we’ll improve the energy performance

We know how to make your buildings more energy efficient without costing you more to build (in fact a lot of our suggestions are likely to make it easier or cheaper) Whether you’re going for full Passivhaus, or just want to make an improvement we can help.   Why are we doing this? We understand spending money in the early days of a project is usually at risk, but this is where the greatest impact (and true value engineering) can take place.  So we’re doing it for free, with no obligation to employ us later either. Just send us an explanation of the project including an idea of the current energy strategy, along with any drawings, sketches or ideas that are currently on the table. What will I get? We will give you our top 5 design changes to improve thermal performance and comfort.  The intention will be to focus on changes that don’t impact on cost but we may stray from this if we think it’s worth it. Send your projects to (p.s. please be kind to our inbox and use wetransfer or similar) Please note that we can’t guarantee a time-frame, and the suggestions are not based on modelling or calculations but rather an eyeball over the scheme.  We reserve the right to not give advice, in which case we will give a...

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PHPP WARM Results Sheet v6.03 Released

Posted by on Mar 9, 2016 in news | Comments Off on PHPP WARM Results Sheet v6.03 Released

PHPP WARM Results Sheet v6.03 Released

Dear all, We have released version 6.03 of the PHPP WARM Results Sheet, which can be downloaded here:   PHPP WARM Results Sheet v6.07 (204.2 KiB, 5,318 hits) The biggest improvement is that it now works with PHPP 8.4. The other changes are minor, and have all been focussed on making it look nicer 🙂 . Hope you like...

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