For homeowners
Can you do your own heat loss survey? A homeowner's guide
By Sean Williams, founder of Heatworx, software engineer and enthusiastic DIYer · Published October 2026 · 5 min read
If you're anything like me, you probably enjoy having a go at things yourself.
Fixing something on my ancient Mini, stripping and painting the front room, tiling the shower: if there's a job to be done, I'll generally have a crack at it. I do draw the line at work that needs the experience and hard-earned knowledge of a professional, like an electrician or a heating engineer.
But understanding how much heat your home loses? That's something I think every homeowner can, and should, have a go at.
The more you understand about where your house loses heat, the better placed you are to make sensible decisions: whether that's cutting your heating bills, sorting out a room that's never warm, or working out what's involved in switching from a gas boiler to an air source heat pump.
In a roundabout way, that's why I ended up building Heatworx.
How it all started
I'm a software engineer by trade, but I have a few friends who are heating engineers.
Back in 2019, one of them asked if I'd help him work out the heat loss of a house where he was replacing the gas boiler. He had a well-loved Mears calculator (a slide-rule-style tool heating engineers have used for decades) and a well-thumbed copy of the CIBSE Domestic Heating Design Guide.
It wasn't a quick job. We spent a full day measuring the property, and by the time we'd worked through every room, checked the figures and arrived at a heat loss calculation we were both happy with, we'd spent the best part of four days on it.
Being a software engineer, I couldn't help thinking there had to be a better way. The calculations were one thing, but the measuring had been the painful part. Surely there was technology that could do most of that for us?
I had this idea of attaching some sort of scanner to my phone (an Android at the time), walking around a room and having it work out the dimensions for me. I spent a lot of time researching what was out there, and tried a couple of options, but nothing quite fitted the bill.
Then, in 2020, Apple put a LiDAR scanner in the iPhone 12 Pro. That was the breakthrough I'd been waiting for, and I was off developing. Several years and an awful lot of work later, Heatworx is the result.
Why bother?
Perhaps your heating bills seem higher than they should be. Maybe there's a room that's always cold. Or perhaps you're thinking about replacing your gas boiler with a heat pump and want to understand what's involved before you get someone round to quote.
A room-by-room heat loss survey is the right place to start, because it tells you:
- How much heat each room needs on a cold winter day, and which rooms need the most.
- Where that heat is going: through the walls, the windows, the roof, the floor, or draughts.
- What difference insulation, new windows or draught-proofing could make, room by room, before you spend the money.
- Whether your existing radiators could keep up at the lower water temperatures a heat pump runs at, and which ones might need changing.
That last one matters more than most people realise. In a 20°C room, a radiator running with 75°C flow and 65°C return water gives out roughly half as much heat when those temperatures drop to 55°C and 45°C, and far less again at lower temperatures (our guide to flow temperature and delta T has the why). Knowing which rooms might be the problem before an installer visits puts you in a much stronger position.
What it won't do
It won't replace a proper survey by your installer. An MCS-certified heat pump installation needs a compliant heat loss calculation, and the installer is responsible for checking the details and making sure the system is properly designed (our heat pump readiness guide covers what they look for).
The part that takes real experience is working out what your walls and floors are actually made of, which often isn't obvious from looking at them. If you're not sure, say so and let the installer check.
What your own survey gives you is a useful starting point and a sanity check. You'll have a better idea of whether a quote makes sense (so does a five-minute estimate from your gas use), you'll know what questions to ask, and you'll understand what the installer means when they say the back bedroom needs a bigger radiator.
Having a go
That's why Heatworx is free for one survey a month. I want homeowners to be able to try it, learn something about their property and make better-informed decisions without paying just to satisfy their curiosity.
I've tried to make it as simple as possible. If your iPhone or iPad has a LiDAR scanner, you scan each room and the dimensions are done for you; if it doesn't, you measure the room with a tape and type the numbers in. Either way you tell it what your walls, floors, windows and roof are made of, and Heatworx does the calculations using the same CIBSE and MCS methods that professional heating engineers use. Your first survey should take you less than two hours.
You don't need to understand the maths behind it, although if you're curious there's plenty to learn. You might find out something interesting about your home along the way.
So why not give it a go? You've got nothing to lose, and you might learn something that saves you money.