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FOR INSTALLERS · REMOTE SURVEY
What Information Does a Heat Pump Designer Need From an Installer?
Good design starts with good survey information.
- Last updated: September 2026
- Heat Loss Hub · For Installers
A heat pump designer can only work from the information supplied.
If room dimensions are missing, wall construction is unclear, radiators are not identified or plant locations have not been considered, the design either slows down or starts relying on assumptions.
A good survey-to-design handover should give the designer enough information to calculate the property accurately and understand the physical constraints of the installation.
KEY TAKEAWAY
This checklist covers the information normally needed before heat pump design begins.
DESIGN INPUT CHECKLIST
Use this checklist to prepare a project that’s genuinely ready for design before it enters the queue.
When Is a Project Actually Ready for Design?
A project is ready for design when the important information is complete enough for the designer to proceed without hiding major unknowns inside assumptions. That means:
- Property information is clear
- Room dimensions are complete
- Construction is understood
- Windows and doors are recorded
- Emitters are identified
- Pipework information is available where required
- Plant locations are known
- Electrical constraints are understood
- Photos or videos support the survey
- Important customer or site restrictions are recorded
- Any assumptions are visible and justified
KEY TAKEAWAY
Missing information should create a query, not an invisible assumption. A project does not need every possible detail before any calculation can begin, but critical unknowns should be resolved before the final design is treated as complete.
Property and Project Basics
Start with the basics. The designer will normally need:
- Property address
- Project reference
- Property type
- Approximate age
- New build, retrofit, renovation or remedial project
- Current heating system
- Number of occupants
- Intended project scope
- Any known extensions or major alterations
- Preferred heat pump manufacturer or model where relevant
The type of project affects the information required. A new build with detailed architectural drawings may need a different survey process from a 1930s retrofit with several extensions and an existing microbore heating system.
Room Dimensions
Room-by-room heat loss starts with accurate geometry. For each room, record:
- Room name
- Length
- Width
- Ceiling height
- Floor area
- Room use
- External wall exposure
- Unusual ceiling shapes
- Vaulted ceilings
- Voids
- Open-plan connections where relevant
KEY TAKEAWAY
Do not rely only on nominal room names from an estate-agent plan. If the measurements are being used to calculate the heat loss, they need to reflect the actual property.
Building Fabric
The designer needs to understand what separates the heated space from outside or from unheated areas. Typical information includes:
Walls
- Solid wall
- Cavity wall
- Insulated cavity
- Timber frame
- Modern insulated construction
- Extension construction where different
Floors
- Suspended timber
- Solid floor
- Insulated slab
- Floor over unheated space
Roofs and Ceilings
- Loft beneath pitched roof
- Room in roof
- Flat roof
- Sloping ceilings
- Insulation depth or specification where known
Other Fabric Details
- Party walls
- Exposed floors
- Unheated garages
- Conservatories
- Extensions
- Converted lofts
Where different parts of the property were built at different times, do not assume one construction applies everywhere.
Windows and Doors
Openings can have a significant effect on room heat loss. For each relevant window or door, record:
- Width
- Height
- Glazing type
- Approximate age where useful
- Frame type where relevant
- Rooflights
- Patio doors
- French doors
- External doors
If windows have been replaced at different times, their performance may also differ. A photograph can help confirm what has been measured, but it should not replace the dimensions themselves.
Ventilation and Infiltration Information
Heat loss is not only through the building fabric. Ventilation also needs to be considered. Useful survey information can include:
- Extract fans
- Mechanical ventilation
- MVHR
- Open flues
- Chimneys
- Significant draughts
- Known air-leakage issues
- Permanently open vents
- Ventilation systems serving specific rooms
The designer should understand anything that may materially affect the ventilation assumptions used in the calculation.
Radiators and Other Emitters
Every existing emitter that may remain part of the system should be recorded. For radiators, this normally means:
- Room
- Width
- Height
- Depth where relevant
- Panel type
- Convector arrangement
- Towel rail type
- Fan-assisted emitter where present
- Whether it is intended to remain
- Whether replacement is acceptable
- Photograph where useful
Do not record a radiator simply as “double radiator”. The designer needs enough information to identify its output properly.
KEY TAKEAWAY
If a radiator is to be retained, it still forms part of the design.
Underfloor Heating
Where underfloor heating exists or is proposed, record:
- Rooms or zones served
- Heated floor area
- Floor construction
- Floor covering
- Manifold location
- Pipe spacing where known
- Pipe size where known
- Existing or proposed system
- Any zones that will not be heated
- Mixed radiator/UFH arrangement
The useful figure is not always the total room floor area. Furniture, kitchen units, baths, showers and fixed fittings may reduce the active heated area.
Existing Pipework
Where the design includes hydraulic assessment, the designer needs to understand the existing distribution system. Useful information includes:
- Primary pipe sizes
- Distribution pipe sizes
- Microbore where present
- Visible pipe routes
- Approximate pipe lengths where relevant
- Existing pumps
- Zone valves
- Hydraulic separation
- Low-loss headers
- Buffers
- Existing bypass arrangements
- Known restrictions
- Sections intended to remain
Photographs are particularly useful where pipework enters the boiler or heat-pump position, cylinder cupboard, floor voids, loft, manifolds and plant areas.
Hot Water and Cylinder Information
The designer also needs enough information to understand the domestic hot-water requirement. Typical inputs include:
- Number of occupants
- Number of bathrooms
- Baths
- Showers
- Large baths or high-flow outlets
- Existing cylinder size
- Existing cylinder type
- Cylinder location
- Available cupboard or plant-space dimensions
- Whether the existing cylinder will be retained
- Immersion heater information
- Hot-water usage concerns
- Existing hot-water problems
Photographs of the cylinder cupboard should show the available space as well as the cylinder itself.
Proposed Outdoor Heat Pump Location
The designer needs to understand where the outdoor unit could realistically go. Record:
- Proposed location
- Available width
- Available depth
- Available height
- Nearby windows
- Nearby doors
- Boundaries
- Paths
- Light wells
- Drains
- Access
- Wall construction
- Ground condition
- Potential base location
- Condensate and defrost-water route
- Pipe route back into the property
- Distance to indoor plant
Provide both a wider photograph showing the surroundings and closer photographs of the proposed position. A video can also be useful where access or pipe routing is difficult to explain in still images.
Electrical Information
The heating design may also depend on what electrical capacity and routing is available. Useful information can include:
- Meter position
- Consumer unit position
- Supply type
- Single-phase or three-phase where known
- Main fuse information where available
- Existing high-load appliances
- EV charger
- Electric shower
- Solar PV
- Battery storage
- Existing immersion heaters
- Proposed cable route
- Distance from consumer unit to heat pump
- Photographs of meter and consumer unit
The heat-pump designer does not replace the electrician or DNO process, but good electrical information can identify obvious constraints before equipment is finalised.
Plans, EPCs and Other Documents
Existing documents can reduce survey work. But they should be used appropriately.
Architectural Plans Can Help With
Room layout, dimensions, floor areas, window and door locations, new-build construction, extensions and proposed layouts. Plans are particularly useful for new builds and major renovations. However, drawings should still be checked against the actual property where relevant.
EPC Information Can Help With
Approximate property age, broad construction type, insulation history, glazing background and existing heating information. An EPC is useful background evidence. It is not automatically a substitute for a room-by-room design survey.
Other Useful Documents
These may include window schedules, construction specifications, structural drawings, UFH drawings, existing heating schematics, previous heat-loss reports, manufacturer designs and electrical information.
Plans and EPC data can support the design, but they do not automatically replace site verification.
Photos and Videos
Good photographs reduce ambiguity. Bad photographs create more questions. Useful survey photography should normally include both context and detail. For example:
Outdoor Unit Position
Take a wide view of the whole area and a closer view of the proposed location.
Radiator
Show the complete radiator, valve arrangement where useful and nearby restrictions.
Cylinder Cupboard
Show the cylinder, surrounding pipework and usable cupboard space.
Consumer Unit
Show the complete board and readable labelling where possible.
Loft
Show insulation, roof structure, access and relevant pipe routes.
Videos can be particularly helpful for explaining pipe routes, plant rooms, loft spaces, outdoor-unit locations, complex access and routes between different parts of the property.
The aim is not to collect hundreds of random images. It is to collect evidence that answers a design question.
Explore: Heat Pump Survey Photo Checklist
Known Site and Customer Constraints
The designer should know about restrictions before the design is produced. Examples include:
- Customer refuses radiator changes in a particular room
- Outdoor unit can only go in one location
- Cylinder cupboard cannot be enlarged
- Pipework cannot cross a particular area
- Finished floors cannot be lifted
- External appearance restrictions
- Planning concerns
- Noise concerns
- Listed building constraints
- Access limitations
- Specific equipment preference
- Required completion date
- Rooms being altered later
KEY TAKEAWAY
These are design inputs. If the designer does not know about them, the technically correct design may still be impossible to build.
Preferred Equipment Is an Input, Not the Answer
Installers often have preferred manufacturers. That is perfectly reasonable. You may prefer a particular heat pump range, cylinder manufacturer, control system, radiator supplier or hydraulic arrangement. The designer should know those preferences.
But the preference should still be checked against the project. The survey should not start with:
“This house needs an 8kW heat pump.”
That is an output of the design. Instead, provide:
“We normally use Manufacturer X and would prefer to use that range if a suitable model is available.”
The designer can then check the actual equipment against the calculated requirements.
KEY TAKEAWAY
The survey should describe the property and constraints. It should not pre-design the answer.
What Can Be Assumed and What Should Be Verified?
Not every design input will always be visible. Sometimes reasonable assumptions are necessary. The important thing is that assumptions are identified, defensible, consistent with the available evidence and reviewed where better information becomes available.
Information That May Sometimes Require an Assumption
Examples might include hidden wall insulation, inaccessible floor construction, exact pipe length and concealed pipe routes.
Information That Should Normally Be Verified Where Practical
Examples include room dimensions, window dimensions, radiator sizes, proposed outdoor-unit location, cylinder-space dimensions and visible pipe sizes.
The distinction depends on the project. The important principle is that a critical assumption should not be hidden as though it were a measured fact.
What Should Stop the Design From Starting?
Some missing information is minor. Some is fundamental. Examples of issues that may need resolving before design progresses include:
- Missing room dimensions
- Unknown construction that materially affects heat loss
- Conflicting drawings and survey measurements
- Windows not measured
- Radiator type or size cannot be identified
- No proposed plant location
- Cylinder space unknown
- Major pipework route cannot be assessed
- Essential photographs missing
- Customer restrictions not confirmed
If those points affect the design materially, the correct response is to raise a query. Not to hide the problem inside an assumption.
KEY TAKEAWAY
A project should not become “design complete” by hiding critical unknowns inside assumptions.
Is the Project Ready for Design?
Use the following checklist before submitting the job.
Property
- Address confirmed
- Property type confirmed
- Project type confirmed
- Room layout understood
- Room dimensions complete
- Ceiling heights recorded
Building Fabric
- Wall construction identified
- Floor construction identified
- Roof/loft construction identified
- Insulation information recorded where available
- Extensions or different construction types identified
Windows and Doors
- Relevant openings measured
- Glazing information recorded
- External doors recorded
- Rooflights recorded
Emitters
- Every existing radiator recorded
- Radiator type identified
- Radiator dimensions recorded
- UFH zones identified
- Retained/replaced emitters clear
Pipework
- Existing pipe sizes recorded where required
- Microbore identified
- Main routes understood
- Important restrictions recorded
Hot Water
- Occupancy recorded
- Existing cylinder identified
- Cylinder location recorded
- Available plant space understood
- Bath/shower demand considered
Heat Pump Location
- Proposed outdoor-unit location identified
- Clearances understood
- Access recorded
- Pipe route understood
- Defrost-water route considered
- Relevant photos supplied
Electrical
- Meter position recorded
- Consumer unit recorded
- Supply information available where possible
- Proposed electrical route understood
- Relevant photographs supplied
Evidence
- Required photographs supplied
- Videos supplied where useful
- Plans attached where available
- Conflicting information resolved
Constraints
- Customer preferences recorded
- Site restrictions recorded
- Planning/noise concerns identified
- Preferred equipment noted where relevant
Status
- No critical information missing
- Important assumptions declared
- Current survey information identified
- Project ready for design
KEY TAKEAWAY
No critical gaps → ready for design.
What Happens When Information Is Missing?
Missing information does not necessarily mean the whole project has to restart. The normal process should be:
- Query raised. The designer identifies the missing or conflicting information.
- Information requested. The installer, surveyor or customer provides the missing detail — that might be one measurement, a photograph, a construction detail, a radiator dimension or a plant-space dimension.
- Information checked. The new information is reviewed against the existing survey.
- Design continues. Once the critical point is resolved, the calculation or design can continue.
Where an assumption is appropriate, it should be recorded rather than hidden.
KEY TAKEAWAY
A structured survey process reduces the number of queries required.
How Remote Survey Support Fits In
The same design information is required whether it is collected during a traditional site survey, by an installer, by a dedicated surveyor, from architectural plans or through a guided homeowner survey.
The challenge is collecting it consistently.
Heat Loss Hub is developing a structured remote-survey process designed to guide the person completing the survey through the information required before a project reaches the designer. That can include measurements, construction, windows and doors, radiators, pipework, cylinder, outdoor-unit location, electrical information, photos and videos.
KEY TAKEAWAY
The objective is simple: make the project complete enough to design before it enters the design queue.
Frequently Asked Questions
Not always. Accurate room measurements can be used where plans are unavailable. However, good floor plans can make the design process easier and help clarify room layout and dimensions.
An EPC can provide useful background information, but it should not normally be treated as a complete substitute for a room-by-room design survey. Additional dimensions, emitter information and physical site details are usually required.
The designer will typically need room dimensions, ceiling height, window and door dimensions and enough information to understand which surfaces are exposed.
Record the radiator dimensions and type. Where practical, provide a photograph and identify whether the radiator is intended to remain or be replaced.
If the design includes hydraulic assessment or existing pipework is being retained, pipe size information can be very important.
Useful information can include the meter position, consumer unit, supply type where known, existing significant electrical loads and the likely route to the heat pump.
Not necessarily. Photographs should answer useful design questions rather than simply create a large image library. Some rooms or features may need more photographic evidence than others.
Potentially, yes. A structured guided survey can allow homeowners to collect measurements, photographs and other information where appropriate. The information still needs to be suitable for design use.
The designer should raise a query where the missing information materially affects the design. The project can continue once the required detail is provided.
Sometimes assumptions are necessary. They should be reasonable, clearly recorded and replaced with verified information where that information becomes available.
No. You can state preferred manufacturers or models, but final equipment selection should follow the calculated design requirements.
Often, particularly on new-build and major renovation projects. However, additional information may still be required for plant locations, pipework, electrical routes, emitters and other site-specific constraints.
Want a Cleaner Survey-to-Design Handover?
A good design process starts before the calculation begins.
Collect the right information. Identify the constraints. Resolve the important unknowns. Then submit a project that is actually ready for design.
USE THE DESIGN INPUT CHECKLIST
Use this checklist to prepare a project that’s genuinely ready for design before it enters the queue.
Explore: Remote Survey Guides