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I came to Salford because I needed to buy a place of my own, and it was one of the areas which had houses for sale that I could afford. Manchester also had an airport which was important for my overseas work assignments.
I decided to do the refurb on the house for several reasons. While I suppose I am fairly environmentally-minded, I guess a large part of why I did the refurb was that the house was damp and dark when I bought it, and parts of the house (e.g. the bathroom) were freezing in cold weather, and I decided that I didn’t want to live in a place like that. In any case, 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 only thing was that 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.
The house is a mid-terrace, that was not well looked after. There was a tenant in the property prior to my arrival, but the house was damp and dark, with daily condensation on the single-glazed windows that were sitting in rotting frames, and slugs on the bread board in the morning.
– Insulation – the house was haemorrhaging heat, and after the insulation went in, it took very little time for the air to warm up in the house.
– Air tightness – although I would use membranes and tapes properly if I did it again, for sure the house became more airtight after I worked on it. I used expanding foam to plug all the nooks and crannies I could find, and although it’s not a good airtightness strategy, I’m sure that it has improved comfort levels as a result.
– Mechanical ventilation with heat recovery – this keeps the house at a comfortable 40-60% relative humidity, which keeps any mould at bay, although at times the humidity does drop below 40% in winter (the lowest fan speed is just a bit too fast for my house). The ventilation means that odours are taken care of, and that the bathroom dries up within a very short time after taking a shower or bath. It also means that I don’t have to open any windows to ventilate, saving energy.
The main improvements have been a reduction in humidity, a warmer house and better air quality. I had an injected damp course done on the whole ground floor, but what made most difference to the humidity (measured by how much condensation was on the windows) was dealing with the evaporation of water from muddy ground below the ground floor (through putting a type of gravel down, covered with plastic) – this cleared up the condensation overnight. In addition to that, I draught-proofed the whole ground floor to prevent air leaking from the crawl space into the living areas. Humidity from other sources (e.g. bathroom, breathing, cooking) is now also kept in check also by the ventilation system that extracts moist stale air and replenishes with air from outside. The humidity in the house now averages between 40 and 60% and I find that in winter when temperatures outside are lower, the system gets more efficient at reducing humidity in the house compared to summer. Regarding temperature, the house is much quicker to heat up than before due to the wall & floor insulation and draught-proofing – meaning I don’t spend much on gas.
I have three favourite parts rather than just one, since I know that these aspects go together to be effective: insulation, draught-proofing and ventilation.
Eric Fewster is a Certified Passive House Consultant specializing in retrofit work in the UK. Using proven Passive House methodology as well as thermal bridging analysis, he can help homeowners plan exactly what energy efficiency measures to carry out in order to achieve specific energy or carbon reduction targets.
The action plan is not only the result of the energy analysis – it also includes a likely list of materials needed, sequence of work & economic analysis, which is all arrived at through several trial runs in consultation with the homeowner. In specific cases, he also takes on the role of project manager (see past projects here).
Eric joined the SuperHomes network after renovating his own house in Manchester, which resulted in reductions of 69% and 60% for space heating demand and carbon emissions respectively. He subsequently trained to be a Passive House Consultant with the aim to help other people in similar situations.
I didn’t do a final air test, but had one done once most insulation and airtightness was done, and the result was 7.85 m3/m2/hour (that is the UK method for measuring leakiness) which translates to about 9.3 air changes/hour (m3 of air compared to volume of house, which is the Passive House method). This was still leaky because there was a large leak from an open chimney flue and a few other places, so if I redid it, I reckon I’d be somewhere around 3-5 air changes – which isn’t enough. I now know you really need to be somewhere around 1.5 air changes an hour for the MVHR unit to operate efficiently. So my air tightness wouldn’t have been good enough, it needs a lot of attention to detail.
Originally I installed the Xpelair Xcell300. I wouldn’t chose it again, for various reasons. For example, the fan speeds cut out once you reduced it to its minimum, which was still too fast for my house volume. You need fully programmable fan speeds ideally as well as one that is efficient and this unit didn’t come with a 3 way switch as standard. Also the ducting didn’t fit together properly!
In 2013 I installed a Brink Sky300 unit (available via phstore.co.uk) which has the following advantages:
This is not to say that the Brink is without fault – there were a few installation issues (e.g. there is a simpler 4-way control switch which can be connected in place of the digital one = simpler to use potentially, except that when it comes time to hoover the filters, the red LED light cannot be switched off without connecting the digital controller to the MVHR unit… in other words better to just install digital controller from the outset; there were also one or two issues with duct connection to the manifold). I’d given feedback on all those points before, so I don’t know if they’ve improved their system yet.
You definitely need to correctly specify the unit given the air flow needed, and the exact amount of ducting/bends will affect the flow rate to each room and this needs to be calculated. So best to get this all designed for you.
No it draws air from inside the house, which works well as air comes in via ventilation system, so there doesn’t seem to be a problem in terms of O2 levels.
I’d recommend doing an energy analysis on the house first and then fit the wall insulation work into a retrofit project that might include other measures while you’re at it. This is because wall insulation of external-facing walls will most likely be a major contributor of heat loss and carbon emissions, but it might not be the biggest factor. If space heating demand or carbon emissions are your main driver for wanting to do the work, then you need to be sure you’re targeting the right thing(s). Also depending what your goals are, if comfort is a big driver for you wanting to do this work, then airtightness and ventilation will be a major contribution to feeling comfortable, not insulation alone.
Also if you’re doing internal wall insulation, you really need to get the airtightness right on the internal face – any gaps will mean moisture can get through and cause interstitial condensation on the cold original wall surface leading to mould (e.g. from modeling and field tests, we know that a typical 1mm gap in air membrane that is 1m long can allow 360g of water to condense – this is with conditions of 20 deg C inside and 50% relative humidity, and 0 deg C outside with 80% relative humidity). So it really kind of links in to other parts of a retrofit and I’m not sure it should be done in isolation without airtightness/ventilation.
The gravel was called ‘MOT’ – don’t know what it stands for but you get it from builder merchants like Travis Perkins. I put down about 5cm depth all over the crawl space, which equated to about 4.5 metric tonnes! I don’t know exactly what type of infill it is, but it tends to soak up moisture a bit, so it helped to make a dry-ish base on which to stand and sort out my joists before putting the DPM down.
The humidity was sorted overnight after the plastic sheet went down, even with all the floorboards up and joists exposed. I know this because I’d get condensation on the windows every morning and the morning after there was none. It just showed that a lot of moisture was coming from evaporation from the ground. Also I know this because the underside of the original chipboard floor was covered in white mould except for the place where it went over the base of the hearth – here there was no mould. Again confirming that evaporation from ground was a big issue.