Category: Building physics

Can I fit a heat pump? What do I need to know?

At the start of 2022 we finally got rid of the gas supply to our home, and retrofitted an air source heat pump. With the high proportion of renewables in grid electricity now, this has led to an absolutely huge cut in our household carbon emissions, and we are delighted with how it has performed so far.

picture of a heat pump
Our Mitsubishi Ecodan

While we were planning this, I wanted to know more about what the process entailed and what we would need to think about – so I decided to write an article about it. I learned so much that I ended up writing a two-parter. Continue reading “Can I fit a heat pump? What do I need to know?”

What is thermal bypass, and why does it matter?

I am greatly indebted to the meticulous working and thinking of architect Mark Siddall (LEAP architecture) here. He’s been talking about thermal bypass for a while, so I asked him to walk me through the basics.

What the term ‘thermal bypass’ means is cold air (usually cold – though of course in summer it could be too hot instead) washing through building fabric, and undermining the thermal performance.

This means that in winter, cold air may be moving around in the walls and roof and taking heat from indoors, even if it doesn’t actually break through any air barriers. A classic example is when insulation is loosely bunged into a cavity, and warm air behind the inner leaf is drawn away and replaced with cold, when it should be held snug against the fabric.

My interview with Mark and some explanations and examples were written up for SIGA, and you can read them here.

A leaky fabric is no substitute for ventilation

In some corners of the construction community there is still a lurking belief that a leaky fabric is needed in order to ensure good indoor air quality.

But gaps and cracks are random, and the air flow through them, even more so. Believing a leaky fabric will contribute usefully to indoor air quality is an act of blind faith. Continue reading “A leaky fabric is no substitute for ventilation”

Cotswold stone warehouse becomes Enerphit hostel

The Barrel Store; once a warehouse, now a super-low-energy hostel: photo courtesy New Brewery Arts / The Barrel Store. Photography by Max McClure

This 150-odd-year old historic stone warehouse in the centre of Cirencester has been very carefully converted to create a youth hostel, providing much-needed budget accommodation in this pretty Cotswold town.

An Enerphit retrofit lifts the comfort way above the usual draughty-old-house-that-was-impossible-for-the-owners-to-heat that may be many people’s experience of UK youth hostels. Continue reading “Cotswold stone warehouse becomes Enerphit hostel”