SettingsSettings for this calculationUS
The VAV terminal's airflow rate at the reheat condition.
This is typically the terminal's minimum (heating) airflow setpoint, since reheat is usually staged in at reduced airflow to avoid overcooling the space.
The desired air temperature increase across the reheat coil, from entering to leaving air.
Set this to the difference between the supply air temperature entering the terminal and the desired leaving air temperature needed to meet the space heating load.
Required reheat coil sensible capacity
25,900 BTU/hr
This is a simplified sensible-heat sizing check using the standard-air 1.08 factor — it is not a substitute for full manufacturer coil selection, which also accounts for entering water/electric element temperature, coil rows, fin spacing, and actual air density (the 1.08 factor itself shifts at high altitude).
They open the calculator with your figures already in it
VAV Terminal Reheat Coil Sensible Heat Capacity Calculator: 25,917 BTU/hr — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Show calculation logicHide calculation logic
How this was calculated
Formula source(s)
- Q(Btu/hr) = 1.08 x CFM x deltaT, the standard ASHRAE sensible heat formula for air at standard conditions (60 min/hr x 0.075 lb/ft³ standard air density x 0.24 Btu/(lb*F) specific heat of air is approximately 1.08). This is a simplified sizing/balance check; full VAV reheat coil selection also accounts for entering water temperature, coil rows, fin spacing, and actual air density at altitude.
Inputs used
- Airflow
- 600 CFM
- Target Temperature Rise ΔT
- 40 °F
Confidence note: This is a simplified sensible-heat sizing check using the standard-air 1.08 factor — it is not a substitute for full manufacturer coil selection, which also accounts for entering water/electric element temperature, coil rows, fin spacing, and actual air density (the 1.08 factor itself shifts at high altitude).
What this calculation does not cover
- The temperature rise is not a free choice, and nothing here stops you entering one the room cannot use. Air leaving a ceiling diffuser much more than about 15 °F (8 °C) above room temperature stops mixing and stratifies at the ceiling — ASHRAE 62.1 penalizes a zone's air distribution effectiveness for exactly that condition. A large rise on a small minimum airflow therefore buys a capacity that heats the plenum while the occupied zone stays cold, and the remedy is more airflow, not more rise.
- Nothing here sizes what feeds the coil. The same duty is either an electric element pulling a breaker and a feeder off a panel, or a hot-water coil demanding a flow rate through a control valve — and across a floor of thirty terminals the summed electrical demand, or the pump flow and pipe size to serve them, is a design quantity in its own right that a per-box capacity never adds up.
Add the equipment this sizes
This result is a specification — 25,900 BTU/hr — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.1.1
Regulatory standards & verification citations1
- Q(Btu/hr) = 1.08 x CFM x deltaT, the standard ASHRAE sensible heat formula for air at standard conditions (60 min/hr x 0.075 lb/ft³ standard air density x 0.24 Btu/(lb*F) specific heat of air is approximately 1.08). This is a simplified sizing/balance check; full VAV reheat coil selection also accounts for entering water temperature, coil rows, fin spacing, and actual air density at altitude.
Cite this page
Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.