External insulation. Saver of energy or destroyer of old buildings. Serious homework

My village. rich in landscape, culture and people.

My village. rich in landscape, culture and people. Challenges with energy efficiency and being fit for the future

Well I am taking the plunge and going for a thermal jacket on my old house. I have what I would call a hybrid house. In 1870 a stone, lime and slate roofed farmhouse was built with 800mm thick walls, no foundation and lots and lots of chimneys next to an existing stone barn. In the 1980’s sometime the house was refurbished. DPC and new concrete floors, fair bit of structural work to the main elevation (large area of brick installed). It was re-rendered in Portland cement, new windows with cavities under them and so on. Mr Jones here moved in 2002. Collapsed stone barn was removed and extension built (cavity wall and the usual). Roof was insulated, windows repaired, boiler changed, PV installed and so on. But I have been sitting on the fence now for quite a few years. I have a plenty full supply of thermal images of all the heat leaving the house. what to do, what to do? I have now taken the plunge because of an opportunity. The nature of my mucked around with house means i can not return it to what once was because of a 100 years or so of mucking around. I now have to take this house forward into this century but also not create a problem for those following. Will my decision end up rotting the house from under me, create and unhealthy interior, compromise the aesthetics, create a maintenance problem 20 years down he road? This is where most of the housing stock in Wales is at? we are one of the most fuel poor nations in Europe and have one of the best stock (I mean best in aesthetic terms) housing. Cladding all this could be potential time bomb but fuel poverty is very real. I plan on installing RH monitors, use the real-time data from my smart meter, drill the wall and fit RH sensors deep in the wall especially in the attic to see what happens to my purlins.

The whole village is gearing up for an energy efficiency onslaught. I have been in discussion with Bangor University of undertaking a post occupancy assessment. Lets see!

The whole village is gearing up for an energy efficiency onslaught. I have been in discussion with Bangor University of undertaking a post occupancy assessment. Lets see!

The opportunity I mentioned is something called Arbed 2 which is Welsh government initiative for the most fuel poor areas to benefit from full funding for energy efficiency measures. Whole streets in the village are scaffolded, scores of boilers, windows, hot water systems are on order. The military like operation is gearing up for a frantic whole village change in the next few months… as usual several more blogs on this

i have been around looking at houses recently upgraded in the area?  Will the insulated house on the left create a damp problem for the one on the right because of the difference in thermal performance?

The village of  Carmel. I have been around looking at houses recently upgraded in my area? Will the insulated house on the left create a damp problem for the one on the right because of the difference in thermal performance on the join? The metal detailing under the gutter and sill extensions, what is the durability like? Will they be cheaper to heat?

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4 Responses to External insulation. Saver of energy or destroyer of old buildings. Serious homework

  1. Cladding the houses externally if correctly detailed and installed is likely to be less of a time-bomb than attempting to insulate them internally.
    Only if the house is gutted, so that the internal insulation can be installed on the inner face of external walls continuously through floor heights, under the ground floor, inside the roof structure, returning on the party walls for a good metre, can internal insulation be advised ; it must also be fully vapour-permeable AND continuous mechanical ventilation needs to be installed to maintain the relative humidity internally at or below about 55%. Then, to avoid leaving structure buried in what are now even colder, wetter walls, in essence, a new house (floors, internal walls, ceilings) is built inside this insulated box.
    Whereas external insulation can be detailed to enclose the whole structure, reducing wind chill and driving rain penetration. Cheap versions of the detailing (the cill, eaves and verge extensions you mention) leave cold bridges, as will stopping the insulation at the party wall line and above ground level. But if the weathering layer of the external insulation is not ventilated, and the inner wall finish is not vapour-open, there is still a risk that moisture will be trapped in the mass of the wall and in the insulation itself, resulting in increased dampness and mould inside, and possible frost-damage to the weathering layer.
    The most fool-proof type of external insulation is therefore rain-screen cladding over a ventilated cavity, outside a wind-tight breather membrane, over a vapour-open quilt, snug on the wall face. This means the mass wall can dry out towards the outside whatever type of finish exists internally. In every case, controlling the internal relative humidity by mechanical ventilation is necessary.

    It would be really useful if Bangor Uni would monitor RH in the walls post installation: we lack longitudinal studies of retrofit, because research funding has been directed more at new-build and at theoretical modelling, not mass field work. Meanwhile the pace of climate change, and increasing fuel poverty, push us to carry out a vast unmonitored experiment on our housing stock using what are probably less-than-optimal materials and detailing. Imitating traditional styling using rendered finishes rather than rain-screen cladding (of timber, corrugated sheet, enamelled steel, or ceramic panels), means we may have more technical failures in the future than we would if we accepted more radical aesthetic changes.

    • Keith Jones says:

      thanks for this. all of it makes sense. when i have talked detailing it seems that one or two sizes fits all and that the budget does not extend th detailing hwich could be needed. i will go back to the University. i have one exposed gable (the the prevailing wind) which would be good for long term monitoring. I will see if i can get further funding and we could pick on a few houses in the village. thanks again for the comment

  2. Following with interest – thanks. Do keep in touch with resources via my blog – progressive heritage. The longterm ‘damage’ of heritage building stock is a concern in the industry but once recognised proactive measures can be taken.

  3. Neil Lewis says:

    Fantastic opportunity for the village and a chance for positive data to promote this type of street by street deployment throughout Wales. Pob lwc.

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