The 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. I didn’t know much about energy efficiency 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.
This house ended up being registered as one of the SuperHomes pioneer projects which that aimed to provide a peer-to-peer platform to showcase retrofit to others considering doing something similar themselves.
- Dates Of Work: 2008 – 2010
- Treated Floor Area: 70 m2
Whole house retrofit of a mid-terrace house, built c.1900, resulting in 69% reduction in space heating demand and 60% reduction in CO2 emissions.
Who was on the team?
Myself, along with various sub-contractors for different tasks
Space heating demand & carbon emissions (before and after according to PHPP)
Fuel Use (before and after)
No data before, as I had just moved in. Data after retrofit does not give accurate picture due to many periods when house has been unoccupied, especially during cold months.
Insulation Improvements
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
Airtightness Improvements
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
Ventilation Improvements
Mechanical Ventilation with Heat Recovery (MVHR) unit installation
- 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.
Door & Window Improvements
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)
Damp Improvements
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)
Heating System Improvements
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 & Electrics Improvements
Appliances
New energy-efficient washing machine, fridge, freezer
Lighting
Low energy CFLs and LEDs in most fittings
Water Improvements
Sink, toilet & bath
Ifö sink, toilet & bath which are designed to save water by design (e.g. toilet flush 2 or 4 litres)
Chimney Improvements
Thermal Bridge Improvements
Fan Test Results
Cost of Project
£40,000, of which:
- 50% was related to energy efficiency work
- 50% was spent on things like new kitchen & bathroom, knocking walls through, carpets, paint, furniture, etc.
Lessons Learned
- Better airtightness using vapour-open materials (e.g. membranes or lime plaster): this was my first renovation, and following advice from a book, my airtightness strategy consisted largely of using expanding foam, which I now know is not an effective strategy. The polythene sheets were also not vapour-permeable, and in any case were not correctly joined together or to walls/floors.
- Wood fibre as insulation for internal wall insulation (avoiding any kind of vapour closed insulation for solid walls), and having WUFI analysis done for the most at-risk wall where u-value would be planned to be under 0.4 W/m2K
- Proper MVHR design prior to procuring unit, to ensure that a lower flow rate can be achieved that would result in 0.3 air changes per hour in winter (to avoid dry air), also to ensure no air flow noise at terminals
- Insulation for kitchen floor prior to concrete being laid
- Better suspended floor insulation stretegy – given what we now know about risk of moisture in joists, I would have taken the joists out and replaced with a recycled glass aggregate floor followed by a lime screed