How to Prepare Your Home for an Air Source Heat Pump: A Complete Guide

Switching to an air source heat pump is one of the most impactful energy upgrades a homeowner can make. But here’s something many people don’t realise until it’s too late: the efficiency of your heat pump depends just as much on your home as it does on the technology itself. A well-prepared home can dramatically reduce your running costs and keep every room comfortable year-round. A poorly prepared one can leave you disappointed — and out of pocket.

This guide walks you through everything you need to do before your air source heat pump is installed, in plain language, with practical advice you can actually act on.

Why Home Preparation Matters So Much

An air source heat pump works differently from a gas boiler. A boiler produces very high-temperature heat — typically between 65°C and 80°C — and can compensate for a draughty, poorly insulated home by simply cranking up the output. A heat pump, by contrast, works best at lower flow temperatures, usually between 35°C and 55°C, and runs most efficiently when it operates steadily over longer periods rather than in short, intense bursts.

This means that if your home loses heat quickly — through thin walls, a poorly insulated loft, or single-glazed windows — your heat pump has to work harder to maintain a comfortable temperature. That extra effort translates directly into higher electricity bills and reduced efficiency.

The good news is that most homes can be made heat-pump-ready with a combination of targeted improvements. You don’t necessarily need to do everything at once, but understanding what’s needed helps you prioritise.

Step 1: Get a Heat Loss Survey

Before you do anything else, arrange a professional heat loss survey. This is a technical assessment carried out by a qualified installer or energy assessor, and it’s the single most important step in the preparation process.

During a heat loss survey, the assessor calculates how much heat your home loses through its walls, roof, floor, windows, and doors. This figure — measured in kilowatts (kW) — determines what size heat pump you need and whether your existing radiators and pipework are adequate.

Without this survey, there’s a real risk of installing a heat pump that’s either too small (leaving you cold in winter) or too large (cycling on and off inefficiently and wearing out faster). A reputable installer will always carry out a heat loss calculation before recommending a system.

What to ask your assessor:

What is the total heat loss of my home in kW?
What size heat pump do I need?
Are my current radiators large enough for lower flow temperatures?
Do I need to upgrade my hot water cylinder?
Are there any insulation improvements that would significantly reduce the required heat pump size?

Step 2: Improve Your Home’s Insulation

Insulation is the foundation of an efficient heat pump system. The better your home retains heat, the less work your heat pump has to do — and the lower your bills will be. Here’s where to focus:

Loft and Roof Insulation

Heat rises, and a significant amount of it escapes through an uninsulated or under-insulated roof. Loft insulation is typically one of the most cost-effective improvements you can make. In most countries, the recommended depth for mineral wool loft insulation is around 270mm, though this varies by region and climate. If your loft insulation is thin, old, or patchy, topping it up is a straightforward job that can make a noticeable difference.

If you have a flat roof or a room-in-roof (where the living space extends into the roof space), the situation is more complex and may require specialist insulation products. Discuss this with your installer.

Wall Insulation

Walls account for a large proportion of heat loss in most homes. The right solution depends on your wall type:

Cavity walls (common in homes built after the 1920s in the UK and similar periods elsewhere): These can usually be insulated by injecting insulating material into the cavity — a relatively quick and affordable process.
Solid walls (common in older homes): These require either internal wall insulation (applied to the inside surface of external walls) or external wall insulation (applied to the outside). Both are more disruptive and expensive than cavity wall insulation, but they can make a substantial difference in older properties.

If you’re unsure what type of walls you have, a surveyor or energy assessor can tell you.

Floor Insulation

Heat loss through floors is often overlooked, but it can be significant — particularly in older homes with suspended timber floors. Insulating beneath a suspended floor is usually achievable by lifting floorboards and fitting insulation between the joists. Solid concrete floors are harder to insulate without raising the floor level, which may not always be practical.

Windows and Doors

If you still have single-glazed windows, upgrading to double or triple glazing will reduce heat loss and improve comfort. However, window replacement is expensive, and the payback period can be long. If full replacement isn’t feasible, secondary glazing or high-quality draught-proofing strips can provide a meaningful improvement at lower cost.

Draught-proofing doors — including letterboxes, keyholes, and the gaps around door frames — is inexpensive and surprisingly effective.

Step 3: Check Your Radiators

This is one of the most commonly misunderstood aspects of heat pump preparation. Many homeowners assume their existing radiators will work fine with a heat pump. Sometimes they will — but often, some upgrades are needed.

Here’s why: your current radiators were probably sized to work with a boiler running at 70°C or higher. A heat pump typically delivers water at 45°C–55°C. At lower temperatures, a radiator produces less heat output. To compensate, you either need larger radiators, more of them, or a combination of both.

Your heat loss survey will identify which radiators are undersized. In practice, many homes only need to upgrade a handful of radiators — often in the largest rooms or those with the most external walls. It’s rarely necessary to replace every radiator in the house.

Practical tips for radiators:

Bleed all radiators before the heat pump is installed to remove trapped air.
Check that thermostatic radiator valves (TRVs) are working correctly and not stuck.
Consider replacing old, small radiators in key rooms with larger, modern ones.
Make sure radiators are not blocked by furniture, curtains, or other obstructions.

Step 4: Consider Underfloor Heating

If you’re planning a significant renovation or building an extension, underfloor heating (UFH) is an excellent partner for an air source heat pump. UFH works at very low flow temperatures — typically 30°C–40°C — which is exactly where heat pumps operate most efficiently.

There are two main types:

Wet underfloor heating: Pipes are embedded in the floor and connected to the heat pump’s water circuit. This is the most efficient option and works particularly well with heat pumps.
Electric underfloor heating: Uses electric heating elements under the floor. This is easier to install in existing homes but is generally more expensive to run and is not connected to the heat pump system.

If you’re retrofitting UFH into an existing home, wet systems can be installed under certain floor types, though it’s more complex than in new builds. Discuss the options with your installer.

Step 5: Upgrade Your Hot Water Cylinder

Most air source heat pumps heat domestic hot water indirectly, using a hot water cylinder. If your home currently has a combi boiler with no cylinder, you’ll need to install one — this is a significant consideration in terms of space and cost.

If you already have a cylinder, it may need to be replaced with a larger, well-insulated model designed for use with heat pumps. Heat pump cylinders are typically larger than standard cylinders because the heat pump heats water more slowly than a boiler.

Key points about hot water cylinders for heat pumps:

A cylinder capacity of 200–300 litres is common for a family home, though the right size depends on your household’s hot water usage.
The cylinder should be well-insulated to minimise heat loss.
It should be compatible with the heat pump model you’re installing.
Your installer will need to ensure the cylinder is located close enough to the heat pump to minimise pipe runs.

Step 6: Prepare the Outdoor Space

The outdoor unit of an air source heat pump needs to be positioned carefully. It draws air from its surroundings, so it needs adequate space and airflow to work efficiently. Here’s what to consider:

Space: The unit needs clear space around it — typically at least 0.5–1 metre on the sides and rear, and more in front where air is expelled. Check the manufacturer’s specifications for the exact requirements.
Airflow: Don’t position the unit in an enclosed space, a corner, or anywhere that restricts airflow. Recirculation of expelled cold air back into the unit significantly reduces efficiency.
Noise: Heat pumps produce some noise — similar to a quiet air conditioning unit. Position the unit away from bedroom windows (yours and your neighbours’) where possible. Check local planning regulations, as some areas have restrictions on noise levels.
Access: The unit will need periodic maintenance, so make sure it’s accessible.
Ground surface: The unit is typically mounted on a concrete pad or anti-vibration feet. Your installer will advise on the best base for your situation.

Step 7: Check Your Electrical Supply

Air source heat pumps run on electricity, and they require a dedicated electrical circuit. Before installation, an electrician should assess your home’s electrical supply to confirm it can handle the additional load.

In most modern homes, the existing consumer unit (fuse box) can accommodate a heat pump with the addition of a new circuit. In older homes, the consumer unit may need to be upgraded. This is worth checking early, as electrical work can add to the overall cost and timeline of the project.

If you’re also considering installing solar panels, this is a good time to plan how the two systems will work together. Solar panels can offset some of the electricity used by the heat pump, reducing running costs further.

Step 8: Research Available Grants and Incentives

Before committing to any work, research what financial support is available in your country or region. Many governments offer grants, subsidies, or tax incentives to encourage homeowners to switch to heat pumps. These schemes change regularly, so it’s important to check the current situation in your area.

In the UK, for example, the Boiler Upgrade Scheme has provided grants to help offset the upfront cost of heat pump installation. Similar schemes exist in other countries, though the amounts and eligibility criteria vary. Your installer should be familiar with the schemes available in your area and can help you apply.

Quick Preparation Checklist

Task	Priority	Notes
Heat loss survey	Essential	Do this first — everything else depends on it
Loft insulation	High	Cost-effective and impactful
Wall insulation	High	Type depends on wall construction
Draught-proofing	Medium	Inexpensive and quick
Radiator assessment	High	Some may need upgrading
Hot water cylinder	Essential (if no cylinder)	Required for most heat pump systems
Outdoor unit location	Essential	Plan early to avoid complications
Electrical supply check	Essential	May need a new circuit or upgraded consumer unit
Research grants	High	Can significantly reduce upfront costs

Frequently Asked Questions

Do I need to fully insulate my home before installing a heat pump?

Not necessarily. A heat pump can work in a home that isn’t perfectly insulated, but it will be less efficient and more expensive to run. The goal is to reduce heat loss as much as practically possible before installation. Your heat loss survey will help you identify the most impactful improvements for your specific home.

Can I keep my existing radiators?

Possibly. Whether your existing radiators are suitable depends on their size relative to the heat loss of each room. Some radiators may be adequate; others may need to be replaced with larger ones. Your installer will assess this as part of the heat loss survey.

How long does it take to prepare a home for a heat pump?

It depends on what work is needed. Draught-proofing and loft insulation can be done in a day or two. Wall insulation and radiator upgrades take longer. If you’re starting from scratch with a poorly insulated home, allow several weeks for all the preparatory work before the heat pump installation itself.

Will a heat pump work in an old house?

Yes, but older homes typically require more preparation work, particularly around insulation and radiator upgrades. Solid-walled properties can be more challenging and expensive to insulate, but it is achievable. Many older homes across the UK and Europe have been successfully converted to heat pump heating.

Do I need planning permission to install an air source heat pump?

In many countries, air source heat pumps fall under permitted development rights, meaning planning permission is not required — provided the installation meets certain conditions (such as noise limits and distance from boundaries). However, rules vary by country, region, and property type. Always check with your local planning authority before proceeding.

What happens if I don’t prepare my home properly?

A heat pump installed in a poorly prepared home will still work, but it will run less efficiently, consume more electricity, and may struggle to maintain comfortable temperatures in very cold weather. In the worst cases, homeowners end up with higher energy bills than expected and a system that doesn’t perform as advertised. Proper preparation is the best way to protect your investment.

Can I install a heat pump myself?

No. Air source heat pump installation must be carried out by a qualified and certified installer. In most countries, installers need specific certifications to work with refrigerants and to ensure the system is eligible for government grants. Always use a certified professional.

Conclusion

Preparing your home for an air source heat pump isn’t just a box-ticking exercise — it’s the difference between a system that transforms your energy bills and one that disappoints. The steps outlined in this guide — from getting a heat loss survey to checking your radiators, insulating your home, and planning the outdoor unit location — are all designed to help your heat pump perform at its best from day one.

The most important thing you can do right now is book a heat loss survey with a qualified installer. Everything else flows from that assessment. Once you know exactly what your home needs, you can plan the work in a logical order, take advantage of any available grants, and move forward with confidence.

An air source heat pump is a long-term investment in your home’s comfort and energy efficiency. With the right preparation, it’s one that pays dividends for decades.