Location: Bathgate, Central Scotland
Installer: Sean Hogan, Aventus Eco
Solution: Full new-build heat pump system design including room-by-room heat loss calculations, open-loop underfloor heating, volumiser integration and 250L Vaillant hot water cylinder.
Table of Contents
The Oversizing Problem in New Builds
When Gavin began building his family home in Bathgate, he did what most careful self-builders do — he asked for advice.
What he received was confusion.
Different installers quoted different heat loss figures. He was told he needed a 13kW heat pump for a brand-new, highly insulated property.
That immediately raised concerns.
A new build of this specification in Central Scotland should not require that size system.
We reviewed the architectural drawings, ran a full room-by-room heat loss calculation and confirmed what instinct suggested:
The property did not need 13kW.
It required a properly designed 7kW system.
Oversizing a heat pump is not “playing safe.”
It increases cycling, reduces efficiency and locks in higher running costs from day one.
The difference is not the brand of heat pump.
It is the design.
Avoid Oversized Systems in Your New Build
Before committing to equipment size, get a proper heat loss calculation carried out by a Heat Geek trained engineer.
Heat Geek Mastery | MCS Certified | Trusted Across Central Scotland
“Outstanding Service from Aventus Eco Ltd – Highly Recommended! I had been struggling with unusually high electricity consumption—around 50 kWh per day—due to my air source heat pump system. Despite reaching out to multiple companies, including the original installer, no one was willing to help or even respond. That’s when I contacted Sean from Aventus Eco Ltd, and I’m so glad I did. Sean promptly visited my home, conducted a thorough evaluation of all relevant factors, and successfully identified the root cause of the issue. He didn’t stop there—he also provided a detailed report that I could share with the installer and even offered to assist further in resolving the problem. Sean’s professionalism, technical expertise, and willingness to go the extra mile truly set him apart. He is an absolute superstar, and I can’t recommend Aventus Eco Ltd highly enough for anyone facing similar challenges. ”
Designing the System Properly From Day One
This project gave us the opportunity to apply full design discipline from the beginning.
The house was extremely efficient, well insulated, well sealed and built to a high standard.
That meant we could optimise the system rather than compensate for poor fabric performance.
The key decisions:
Full room-by-room heat loss calculations
Underfloor heating pipe layout designed for correct loop lengths
Fully open-loop hydraulic design (no secondary pumps)
Low flow temperature optimisation
Correct system water volume
We worked alongside the underfloor heating contractor to ensure pipe spacing, loop lengths and flow rates were aligned with the calculated heat demand.
Everything was designed around achieving the lowest stable flow temperature possible.
Because lower flow temperature = higher efficiency.
Design Determines Performance
If you’re building in Scotland, start with the numbers, not the equipment list.
Heat Geek Mastery | MCS Certified | Trusted Across Central Scotland
“Exactly as the process should be – right from start to finish Aventus Eco fitted solar panels, battery storage and an air-source heat pump, and the whole experience has been great. There was no hard sell from these guys, just lots of advice from people who clearly care about what they do, their business and their reputation. They took the time to get the design right for my home, including properly working out our power use and heat loss and sizing everything accordingly. ”
Engineering Simplicity: Open Loop & Low Flow Temperatures
Many systems become unnecessarily complex.
Extra pumps. Buffer tanks used incorrectly. Hydraulic separation where it is not required.
In this Bathgate home, we went the opposite direction.
Fully open loop.
The heat pump flow and return connect directly into the underfloor heating manifold.
No additional pumps.
No unnecessary restrictions.
This allows:
Better hydraulic balance
Reduced electrical consumption
Improved seasonal efficiency
We integrated a volumiser to increase system water content, something heat pumps benefit from during defrost cycles and modulation.
The plant room includes:
Underfloor heating manifold with adjustable flow rates per loop
Volumiser for system volume stability
Expansion vessels sized correctly
250L Vaillant Unistor hot water cylinder
Simple. Clean. Efficient.
Keep Your System Simple. Keep It Efficient.
Open-loop design, correct volume and low flow temperatures make the difference.
Heat Geek Mastery | MCS Certified | Trusted Across Central Scotland
“Great experience using Aventus Eco to install a Heat pump at our terraced home. Very efficient from start to finish from Sean & co.; it took 4 days and we’re really happy with how it’s working. Sean also took time to talk us through how it all works and has been on hand to answer any question post-installation. Will be recommending them to friends and family.”
Real-World Winter Performance: 440% Efficiency
This is where design proves itself.
During November:
Outdoor temperatures averaged between 0°C and -2°C.
We saw lows of -5°C.
The system delivered 440% efficiency (COP 4.4) across the month.
That is in real Scottish winter conditions.
Not brochure numbers.
Not laboratory testing.
Actual performance data.
The home is fully electrified.
No gas.
No fossil fuel backup.
And yet the system maintains consistent internal comfort without high electricity use.
This is what happens when:
The heat pump is correctly sized
The emitters are properly designed
Flow temperature is optimised
System volume is sufficient
Efficiency becomes stable, not forced.
Want 400%+ Efficiency in Real Winter Conditions?
It starts with correct sizing and proper hydraulic design.
Heat Geek Mastery | MCS Certified | Trusted Across Central Scotland
“Great experience from start to finish, excellent customer service and a job well done !”
Winning Over Skepticism
Gavin is a builder.
Like many in the trade, he had heard mixed messages about heat pumps.
There is still stigma around new technology.
Now he regularly explains to other trades on site how the system works and why it performs the way it does.
This project has led directly to further new build enquiries.
When performance is visible, doubt disappears.
Award-Winning Design Is Not an Accident
It’s calculated. If the plan is precise, the installation is easy.
Heat Geek Mastery | MCS Certified | Trusted Across Central Scotland
“Outstanding service, difficult decision to make to change to air source heat pump especially give the level of misinformation. Sean/Aventus Eco were outstanding in helping me explore and decide that this was right solution. Additionally it involved full house re-plumb because of problems with the old system, This was handled sensitively and professionally by all the members of the team with Sean setting very high expectations for everyone. I had hesitated because of the level of disruption but in fact it all went very smoothly. Thank you Sean/Aventis Eco and your team. I have no hesitation in fully recommending Sean and Aventus Eco Ltd.”
Why This Project Won Awards
This installation received:
Best New Build Renewable Heating Project in Scotland by Scottish Energy Efficiency Awards
Awards are recognition, but the real achievement is design precision.
The system was not oversized.
It was not overcomplicated.
It was engineered correctly.
What This Case Study Shows About Modern Heat Pump Design
This project highlights a broader shift in Scotland’s heating industry.
The best new builds are now adopting retrofit discipline:
Accurate heat loss calculations
Right-sized equipment
Low temperature optimisation
Hydraulically simple layouts
Oversizing is not insurance.
It is inefficiency built in from day one.
When you design precisely:
Equipment size reduces
Installation complexity reduces
Lifetime costs reduce
Comfort improves
The result is not flashy.
It is stable.
Even.
Consistent.
Planning a New Build in Scotland?
Before you accept a quoted heat pump size, get an independent design carried out.
Heat Geek Mastery | MCS Certified | Trusted Across Central Scotland
“After calling many companies and having an electrician come and wrongly replace our fit meter, Sean could not have been more helpful. He took the time to help and explained everything so well despite it being a small job. He arranged for an electrician to come and checked in afterwards. I couldn't rate him higher; we are very grateful for his help.”
Contact Aventus Eco
Aventus Eco designs and installs high-performance heat pump systems across Central Scotland.
If you are building a new home or planning a renewable heating system, speak directly to Sean Hogan and the team.
Design determines performance.
Start there.
Ready to find the perfect system for your property?
Get in touch with Aventus Eco and book your Free Survey & Quote Today.
Heat Geek Mastery | MCS Certified | Trusted Across Central Scotland
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