Unpublished Articles
The following are articles that were scheduled for publishing in Selfbuild and Design Magazine in early 2018.
An Introduction to PHPP, Part 2: More about PHPP
Last month we began looking at the Passive House Planning Package, which is available as a workbook for Microsoft Excel (or for the free Calc software). We looked at the first few tabs (or worksheets) and now continue, starting with the fifth tab, U‑Values. Even if the reader is not interested in using PHPP, the factors mentioned below should be borne in mind when designing and building a low energy house.
The PHPP workbook uses some slightly idiosyncratic terminology. In the U-Values tab, we will meet the 'Building assemblies' that make up the thermal envelope: Exterior wall(s), Upper ceiling or Roof, and Ground floor.
An Introduction to PHPP, Part 4: Conclusion
In the preceding three parts of this 'Introduction to PHPP', we have looked at the first twelve tabs (or worksheets) of the Excel workbook called the 'Passive House Planning Package' (PHPP). Those tabs are where most of the user input is required. There remain another 20 tabs to consider, but most of them require little or no user input, and we can deal with all the remaining tabs in this last article.
HRV Units
As we saw last month, Heat Recovery Ventilation gives healthy and energy efficient ventilation.
An HRV system consists essentially of an HRV unit with ducting that channels the airflows around the house. In each room, a duct terminates with an air valve. Fresh air is supplied to the 'dry', habitable rooms – living and dining rooms, bedrooms, etc – and stale air is extracted from the 'wet' rooms – kitchen, bathroom, WC, utility room.
The Design and Installation of a HRV System
HRV components are often supplied direct from the manufacturer (or UK importer). Most suppliers offer to design a system from your architectural drawings. Or you may want to pay for a design. (See, for example, 'Green Building Store' in Further Info.)
The design (and installation) should comply with Approved Document F1 of the building regulations. That stipulates the minimum supply rate, according to the floor area of the house or the number of bedrooms. The supply airflows to inhabited rooms are usually set to be in proportion to room volumes. The Approved Document also sets minimum extract rates for the different types of wet room: kitchen, utility room, bathroom, or WC. Their sum gives the minimum total extract rate that is required – the Boost setting of the HRV unit must be capable of achieving this. (For details, see the Footnote.)
An Introduction to PHPP, Part 3: Windows and their shading, and ventilation
n the first two articles of this introduction to the Passive House Planning Package (PHPP), we have looked at the first 8 tabs of the Excel workbook: Brief Instructions, Verification, Overview, Climate, U-Values, Areas, Ground, and Components.
Reminder: PHPP is an accurate method of calculating the energy performance of a building, and for assessing whether the building meets the criteria for being certified as a 'Passive House' (ie, one that requires very little energy for heating).
We continue with Windows, through which much heat flows, both inwards and outwards.
Heat Recovery Ventilation: For healthy, energy-efficient ventilation
Heat Recovery Ventilation (HRV) is an integral part of the Passive House approach to achieving ultra-low energy houses. In the UK, HRV is often known as Mechanical Ventilation with Heat Recovery (MVHR), but that is too much of a mouthful, and it won't be used again in this article.
The common method of ventilating new houses is by natural ventilation (with trickle vents in windows) augmented by intermittent extract fans,. Like me, you might be attracted to what is 'natural', but leave this inferior method of ventilation to the mass house builders. Selfbuilders do better.
'Build Tight – Ventilate Right' is a much quoted slogan. Many well informed people think that the best way to Ventilate Right is to install a Heat Recovery Ventilation system.
Ducting For HRV Systems: The distribution of airflows
As we saw in my two previous articles, Heat Recovery Ventilation (HRV) gives healthy and comfortable ventilation whatever the weather. And in wintertime, it conserves most of the heat that is generally lost by natural ventilation. The HRV unit, with its two fans and heat exchanger, is at the heart of the system. Now we consider how the airflows to and from the HRV unit are distributed around the house.
Ductwork
The incoming, fresh supply air is distributed via ducting to inlets in the habitable rooms (living room, bedrooms, etc); exhaust air is taken from outlets in the 'wet' rooms (bathroom, WC, etc, and the kitchen).
Two types of layout for ducting are possible, branched or radial.
Sundry Aspects of Heat Recovery Ventilations
In my earlier articles I have described the basics of a Heat Recovery Ventilation system:
The HRV unit, where the exhaust air warms the fresh supply air (or possibly cools it in summertime).
And:
The ductwork and air valves through which the supply and exhaust air streams are conveyed.
To wrap up the series up, here are some diverse observations.
