Eric Fewster

I didn’t know much about energy efficiency when I bought the house, or in what order to do things, so I spent some cash on a few books and read up about what I should do, after which I made a do-list and decided roughly in what order things should be done. When it was all done, looking back I realise that what I had done was a ‘deep retrofit’, and at the time some of it was quite progressive (e.g. putting in MVHR). 

The retrofit was done in phases between 2008 and 2010, after which I realised that I had developed an interest in this area, so I decided to re-train as a Passivhaus Consultant in order to try to better understand building physics, why certain things are done in retrofit and what the better ways were to do them. Since qualifying in 2012, I have been helping people do the joined-up planning for their own retrofit projects (see www.coldproof.co.uK) – this has included not only the energy analysis but also things like ventilation design, thermal bridge modelling, costing, liaising with contractors, even acting as project manager. As always, it’s been (and continues to be) a steep learning curve!  

Realising that very few contractors knew how to do retrofit properly (especially with regards to things like airtightness), I spent the summer of 2018 helping the AECB Carbonlite team to develop training material for a UK-based Passivhaus Tradesperson course (www.passivhaustraining.co.uk/contractor). We ran the first one in October 2018, and since then it has become increasingly popular – by the end of 2021 we had trained close to 700 people. 

Motivations: 

House was damp and dark when I bought it, and parts of the house (e.g. the bathroom) were freezing in cold weather. I had to do a certain amount of things anyway since the house was in a fairly bad state (e.g. window frames were rotten), so I found that this was a good time to try to make it better while I was at it.  

The property is a Victorian mid-terrace house, built c.1900. 

• Bathroom ceiling – Polyisocyanurate (Kingspan) 120mm thick friction-fitted in rafters, u-value 0.321 W/m2K  
• Internal walls (external-facing – i.e. not party walls) – Polyisocyanurate (Kingspan) 70mm thick friction-fitted in studwork, u-value 0.372 W/m2K 
• Suspended timber floor – Polyisocyanurate (Kingspan) 100mm thick friction-fitted between joists, u-value 0.321 W/m2K 
• Loft – Mineral wool 270mm thick, u-value 0.149 W/m2K 
• Bay window ceiling above French doors – Polyisocyanurate (Kingspan) 100mm thick friction-fitted between rafters, u-value 0.332 W/m2K 
• Some vapour-impermeable sheeting, combined with use of expanding foam – Vapour-impermeable polythene sheets used on insulated internal walls and bathroom ceiling, but these were not adequately taped or sealed to create a draught proof barrier. No membrane was used on ground floor – here I only relied on expanding foam. No membrane used on bedroom ceilings. Here I used expanding foam to seal up between plasterboards and wire penetrations via the loft space 
• Mechanical Ventilation with Heat Recovery (MVHR) unit installed – Xpelair Xcell-300 unit installed in loft, 91% heat recovery. Air is extracted from kitchen & bathroom and supplied to 2 bedrooms and lounge via 125mm round/rectangular ductwork and 180mm insulated ductwork in the loft space. 82 m3/hour measured flow rate, which is the lowest flow rate possible before fans cut out – which means ventilation rate of 0.45 air changes per hour. Humidity in house varies within the 40-60% range, but occasionally dips below 40% in winter. 
• New windows and doors – Rehau PVC double-glazed windows and French doors, with 28mm gap argon-filled glazing, u-value of whole window 2.2 W/m2K (glazing u-value 1.5 W/m2K). One Velux wood-framed window in bathroom, u-value of whole window 1.98 W/m2K (glazing u-value 1.1 W/m2K) 
• Ground floor & walls – I had an injected damp course done on the whole ground floor. Kitchen floor had to be drilled up and re-laid (rising damp due to inadequate DPM). Keim Lotexan capillary block added on external face of walls to reduce amount of moisture soaking into the brickwork. 
• Crawl space – Put 4.5 tonnes of MOT (gravel mix) onto the muddy crawl space floor to soak up moisture and deal with mud and unevenness. After that I laid a thick polythene sheeting on top of this to reduce evaporation (cleared up the condensation on windows overnight)  
• Condensing boiler – Replaced old boiler with Remeha Avanta Plus condensing boiler 
• Radiators – New radiators throughout, most with TRVs 
• Wood-burning stove – Løvenholm 5kW HETAS-approved smokeless zone stove put into larger chimney breast on ground floor. Appropriate chimney cowl added to stack 
• Appliances – New energy-efficient washing machine, fridge, freezer 
• Lighting – Low energy CFLs and LEDs in most fittings 
• Sink, toiler & bath – Ifö sink, toilet & bath which are designed to save water by design (e.g. toilet flush 2 or 4 litres)