Ampworth calculators

Heat pump noise assessment

heat_pump_noise

Read-onlyIdempotent

Calculate the sound pressure level an air source heat pump produces at an assessment position, and whether it meets the 37 dB(A) permitted development noise limit, using the method in MCS 020.

The formula is Lp = Lw + 10 log(Q / 4.pi.r^2) - Ab.

Lw is the A-weighted sound POWER level of the unit from its product fiche, energy label or the MCS product database. This is not the sound pressure level, which is a smaller number that already has a distance built into it; confusing the two produces an answer that is wrong by about twenty decibels. The figure for low noise mode must not be used.

Q is the directivity factor, from the count of reflecting surfaces within one metre of the unit that extend at least a metre past it in two or more directions. The ground counts; vegetation does not. One surface gives Q=2, two gives Q=4, three gives Q=8. More than three cannot meet MCS 020 at all.

r is the straight-line distance in metres to the assessment position, which is a window or door of a habitable room in a NEIGHBOURING property, at any floor. Every affected position must be checked separately, and the nearest is not always the worst.

Ab is the barrier attenuation. Fences with gaps, and vegetation of any kind, count as no barrier.

Where several units serve one position, list them all and they are combined logarithmically.

Method from MCS 020. These calculators follow the published MCS methods, for understanding a system and checking a quotation. Anything that gets installed still needs a design and a site survey from a certified installer.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`units`	Yes	The heat pump or heat pumps being assessed, each with its own distance and barrier to this assessment position. At least one is required.

Output Schema

TableJSON Schema

Name	Required	Description
`limit`	Yes	The permitted development noise limit, 37.0 dB(A).
`notes`	Yes
`units`	Yes
`method`	Yes
`verdict`	Yes
`headroom`	Yes	Decibels below the limit. Negative when the limit is exceeded.
`remedies`	No	What would bring a failing position within the limit.
`compliant`	Yes	True when the level is at or below the limit.
`references`	Yes
`soundPressureLevel`	Yes	Combined A-weighted sound pressure level at the assessment position, in dB(A), rounded to one decimal place as MCS 020 requires.

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 16, 2026

TDQS

A4.5/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the readOnly/idempotent/non-destructive annotations, the description discloses genuine behavioral constraints: more than three reflecting surfaces 'cannot meet MCS 020 at all', low-noise-mode figures must not be used, and mistaking Lw for Lp is off by ~20 dB. That is useful failure-mode context, though it stops short of stating assumptions or limitations of the calculation itself.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded purpose sentence, then one short paragraph per formula term, then a scope disclaimer. Long but every section maps to a decision the caller must make (which Lw, which Q, which r, which Ab), and nothing is padding.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present, return values need not be explained. The description supplies the method, the multi-unit combination rule, the pass/fail constraint, and the professional-advice caveat, leaving no gap an agent needs filled before calling.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3; the description earns above baseline by explaining the concepts behind each field (directivity factor Q from reflecting surfaces, r as straight-line distance to a neighbouring habitable room, Ab as barrier attenuation where gaps/vegetation count as none) and by warning about the most common input error.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Calculate the sound pressure level an air source heat pump produces at an assessment position') plus the regulatory test it performs (37 dB(A) permitted development limit, MCS 020). This is unambiguous and clearly distinct from siblings like heat_pump_size or heat_pump_running_cost.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives real operational guidance: 'Every affected position must be checked separately', 'the nearest is not always the worst', and multi-unit handling ('list them all and they are combined logarithmically'). It frames the tool for 'understanding a system and checking a quotation', but never names an alternative tool or states when not to use this one, so it stops short of a 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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