bsmadeezbyjez

Heating

Space Heat Loss

Fabric loss (U·A·ΔT per element) plus ventilation/infiltration loss.

Note: this is the standard simplified method (BS EN 12831). U-values below are just typical starting points for you to overwrite with your actual build-up — I didn't want to guess at figures for a specific "SR50" table since I wasn't sure which standard you meant. Tell me and I'll tune this.

Fabric loss

ElementU-value (W/m²K)Area (m²)Loss (W)

Ventilation / infiltration loss

m³
°C
°C
Fabric loss
–
Ventilation loss
–
Total heat loss
–

Method: Fabric: Σ(U×A×ΔT). Ventilation: 0.33 × ACH × Volume × ΔT (0.33 Wh/m³K ≈ ρ·cp of air). ΔT = internal − external design temp.

Further reading (CIBSE) Guide A: Environmental Design — fabric performance & heat loss methods Guide B1: Heating — system design

Water Services

Pipe Sizing

Flow rate in, velocity and Pa/m out — circular or rectangular, metric or imperial.

Method: Darcy-Weisbach + Colebrook-White (laminar below Re 2300 uses f=64/Re). Rectangular sections use hydraulic diameter for the friction calc. Roughness values are typical starting points — verify against your project spec.

Further reading (CIBSE) Guide G: Public Health and Plumbing Engineering — water services design Guide C: Reference Data — pipe sizing spreadsheets & fluid properties

Ventilation

Duct Sizing

Flow rate in, velocity and Pa/m out — circular or rectangular, metric or imperial.

Method: Darcy-Weisbach + Colebrook-White. Rectangular ducts use hydraulic diameter (2ab/(a+b)) for the friction calc — a good approximation for most aspect ratios; very flat/elongated ducts want CIBSE Guide C's additional aspect-ratio correction, not yet included.

Further reading (CIBSE) Guide B2: Ventilation and Ductwork Guide C: Reference Data — duct sizing spreadsheets

Refrigeration & Heat Pumps

Heat Pump / AHU / Chiller Duty Calculator

Pick what you're sizing first — the right fields show up for it.

Scope note: this doesn't model actual refrigerant properties (P‑h enthalpy data for R32/R410A/R290 etc. is proprietary/complex and varies by manufacturer selection software) — it works off duty and COP/EER, which covers most day-to-day sizing checks. If you want true refrigerant-side mass flow, that needs a manufacturer's selection tool.

What are you sizing?

Pricing

Upgrade your plan

Every calculator stays free. Pro adds the stuff that saves you re-doing work.

Heads up: this is the pricing page laid out and ready to go — there's no payment processing wired up yet (that needs a backend, e.g. Stripe, once you're ready to actually charge). Right now "Upgrade" just captures interest via email below.
Current plan

Free

All calculators, full precision, no limits on use.

  • Heating, Water Services, Ventilation & Refrigeration calculators
  • Ireland supplier finder + datasheets
  • Metric & imperial units
£4.99 / month

Pro

For when you're running this across real projects, not just one-off checks.

  • Save & export calculations as a PDF report
  • Multiple saved projects, come back and edit later
  • Custom U-values, roughness & cable data saved as your defaults
  • Priority on new calculators you request

Get notified when Pro launches