Guides

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, 2,489 hits)   Glazing Frame Specifications for Passivhaus (87.0 KiB, 2,203 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, 2,489 hits) Excel sheet (fill this out and upload to your website):   Glazing Frame Specifications for Passivhaus (87.0 KiB, 2,203...

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New PHPP Guide: Formulae to Make Solid Shading Transparent

Posted by on Nov 9, 2015 in Guides, news, Of interest | Comments Off on New PHPP Guide: Formulae to Make Solid Shading Transparent

New PHPP Guide: Formulae to Make Solid Shading Transparent

Dear all, We have published a guide to applying a transparency factor to objects in the shading sheet in your PHPP. Let’s say you are modelling a line of trees in your PHPP. The spreadsheet assumes that they are completely opaque, but this isn’t true – some degree of light always gets through. This guide shows you how to apply some transparency to those trees, making your shading more accurate. It is also useful for modelling non-solid fences, brise-soleils and pergolas. Download link:  PHPP Formulae to Make Shading Transparent (DEPRECATED) (220.1 KiB, 2,708 hits) Hope you find it useful! Liam McDonagh-Greaves,...

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The new residential TFA rules

Posted by on Jan 7, 2013 in Guides | Comments Off on The new residential TFA rules

PHPP Version 7, introduced earlier this year, contains some significant changes with regard to what’s counted as Treated Floor Area (TFA). The UK builds the smallest homes in Europe, and smaller buildings can struggle within the Passivhaus methodology. Unlike the UK convention, where the floor area is taken as everything within the external walls (including partitions and stairs), Passivhaus considers the actual rooms within the home. As the heating energy demand within PHPP is measured per m2 of TFA, a building with a small TFA will generally have proportionally greater heat loss areas (walls floor and roof) than a building with a bigger TFA. Consequently, maximising TFA is important, as is a clear understanding of what’s included, and what isn’t. TFA, as a measure of internal space, comes from the German Verordnung zur Berechnung der Wohnfläche (Wohnflächenverordnung – WoFlV), a standard designed for assessing the space in houses and flats for sale, and not one to put on your Christmas list. As a result of its role, to help home buyers, it penalises areas which don’t fit into a strict definition of ‘usable space’. On mainland Europe, with larger homes, this may not have been too problematic, but we found that in the UK TFA measurements were having a major impact on the viability of designs. The new TFA rules seem to have recognised some of the limitations of the Wohnflächenverordnung and that should make designers lives a bit easier. The residential changes are listed below (non-residential TFA will be covered separately) For floor area to be counted in TFA it has to be within the thermal envelope. Most floor area is counted at 100%, with some areas being counted at 50% or 60%:   Counted at 100% Living areas, bathrooms, hallways, plant rooms and store rooms/cupboards. This includes full height reveals more than 0.13m deep, the areas covered by built in furniture, and flights of stairs with 3 or less steps. The notable changes here are that plant rooms (eg cupboard with a hot water cylinder/ MVHR unit) are now included at 100% stair heads and landings are now clearly included.   Counted at 50% Areas with an internal height between 1m and 2m are included at 50% (in other words a 1m2 space would be entered in the PHPP model as 0.5m2). Understairs cupboards and the eaves spaces in rooms within pitched roofs fall into this category.   Counted at 60% Rooms outside dwellings or in basements are counted at 60%. The rules with regard to basements within houses are quite confusing, but essentially the way spaces are treated depends on whether there are windows. If over half the basement can be classed as a ‘living area’ (which is defined as having a window area greater than 10% of the surface area) then the TFA is counted at 100%. If less than half the basement is classed as a ‘living area’ then access storage and plant areas are counted at 60%. The diagram on page 49 of the PHPP Version 7 manual shows this quite clearly. For multiple occupancy dwellings the big change is that access areas outside dwellings are now included at 60%. This has a significant impact on blocks of flats, where the communal areas were previously ignored with regard to TFA.   We would always recommend double-checking your TFA measurements, particularly for smaller schemes. An over-estimate in this area could cause you a real headache later on when it comes to...

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10 most common PHPP mistakes

Posted by on Oct 25, 2012 in Guides | Comments Off on 10 most common PHPP mistakes

WARM have now certified 21 Passivhaus schemes. We like to see the designer’s PHPP as early as possible so we can perform an initial check. Unfortunately this can sometimes be a painful experience as PHPP offers so many ways to make a mistake, and is rarely forgiving when you do. So I thought I’d go through the top 10 most common (and significant) PHPP mistakes. If you have a project you think you’d like certified we’d be happy to quote for an initial PHPP check as part of our standard certification fee. 1. Entering multiple casement windows in one row It’s ok to enter two identical window casements in a row with a quantity of 2. But, it’s not ok to enter a two casement window in a single row (with a quantity of 1). PHPP will assume it is a single casement, meaning the proportion of frame will be too low, and the heat losses and gains will be wrong. Every time you do this a kitten dies. Actually that’s not true, but it does spoil my day finding it. 2. Heat loss areas don’t match U values Heat loss areas for Passivhaus are measured externally. On a section this is a continuous line running around the outside of the thermal envelope. The question is – what is the outside of the thermal envelope? The easy answer is – the outside of whatever is the outer element in the U value calculation. Take a timber frame wall with a ventilated cavity and rain screen, it is the convention to ignore the cavity and rain screen in the U value calculation – as the thermal performance is unpredictable. In this case the outside of the thermal envelope will be outside of the timber wall – not the outside of the rainscreen.   3. Altitude not entered A proportion of the BRE climate data weather stations are based at between 0 -50m, so there’s a good chance your site is higher. Enter the altitude of your site as soon as you start a PHPP to avoid the dismay of adding a kWh to the heating demand figure when it’s too late to change the design.   4. MVHR external duct data incomplete To take account of the effect of heat loss from the MVHR’s intake/exhaust ductwork PHPP needs to know the duct length, diameter, insulation thickness and conductivity. Designers frequently miss the entry of the duct details – which results in no account being taken of the heat loss. The new PHPP version 7 has made this mistake harder to make, whereas PHPP 2007 hid the ‘secondary calculations’ on the ventilation sheet off the right as if they didn’t really matter. If your MVHR’s effective heat recovery efficiency (big green box) is the same as the unit’s quoted efficiency you have a problem, typically it should be a couple of percent lower. 5. Conductivity entered is not the Lambda 90/90 Most SAP assessors don’t have the time or desire to check manufactures claims, but Passivhaus certifiers do – in fact we love it. So makes sure your conductivities are lambda 90/90 values see BBA’s explanation (pdf download). And question other claims too – from 0.55 U value doors (you know who you are), to tin foil insulation and ventilated cavities on the warm side of insulation. If you want to check something, give us a call. 6. Ventilation rates are too low PHPP frequently calculates a ventilation rate of around 0.3ACH, and warns you if the rate gets over 1.5x the supply air rate. However, this is based on German...

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A guide to Volume Calculations for Passivhaus Air Tightness Testing and the Difference with the UK Method

Posted by on Aug 11, 2011 in Guides | Comments Off on A guide to Volume Calculations for Passivhaus Air Tightness Testing and the Difference with the UK Method

UK Methodology The UK standard measures Air Permeability, in m3/hr/m2@50Pa (the q50 measurement), or in other words the air leakage per square metre of building envelope. The ATTMA (Air Tightness Testing and Measurement Association) TS1 standard defines the building envelope as everything within the air barrier line ‘along the line of the component to be relied upon for air sealing’. This could be anywhere within the building envelope (even the external render). This is a measure of building envelope airtightness. Passivhaus Methodology The Passivhaus standard measures the Air Change Rate (ACH) @50Pa (the n50 measurement), or in other words the number of times the volume of air within the building is changed in an hour. So, it is a purely volumetric measure. The Passivhaus methodology considers the volume of air which needs to be heated. Therefore internal walls and floors are excluded. This is a measure of air infiltration, and hence the heating energy cost of the building. Calculating the Passivhaus Air Test Volume A straightforward way to calculate the volume required for the Pressure Test is as follows: Start with the Treated Floor Area (TFA) Add the space occupied by any stairs (imagine that they do not exist and that a standard floor construction occupies the void) Any areas treated at 60% for TFA purposes should be treated at 100% for this volume calculation The total TFA for each floor can be multiplied by each floor to ceiling height (averaged if necessary for sloping ceilings) to give a volume for each storey (not including internal floors) The total for all the storeys equals the Pressure Test volume Divide the measured air flowrate, in m3/hr, by the Pressure Test Volume (m3) to get the air change rate, n50 Note The two measures, Air Permeability and Air Change Rate, do not have a direct relationship with each other (so you can’t apply a conversion factor to one to get the other). Therefore the building needs to be measured to the right protocol, and the results calculated in the right way (n50 not q50), to get a result which can be used for certification. It is essential to use the correct volume for testing, even before the interior spaces are fully finished. Voids within wall and floor constructions cannot be...

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