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Radiant floor heating, answered with numbers

Short answers and guides, each with one number calculated in HeatAlgo and the conditions behind it.

Planning radiant floor heating for your own home? What to prepare before a quote What a design should include

Guides

Radiant heating glossary for installers: heat loss, U-factor, R-value, delta T

A radiant heating glossary for installers: heat loss, U-factor, R-value, thermal bridges, ACH50, balance point, COP, delta T, outdoor reset and on center.

Guides

Heating glossary for homeowners: what your installer's form asks for

A heating glossary for homeowners: floor plans, sections, window schedules, U-factor, R-value and radiant floor heating - what each is and where to find it.

News

Radiant floor heating from a floor plan: AI draws the sections and loops

Upload a floor plan as PDF, PNG, JPG, HEIC, DWG or DXF, set the scale, and HeatAlgo's AI draws radiant floor heating sections with PEX loop layouts to EN 1264.

Guides

Heat recovery ventilation (HRV) in HeatAlgo (beta): six steps from rooms to the balance and the unit

Design heat recovery ventilator (HRV) systems in HeatAlgo: room airflows in cfm, ducts on floor plans, the unit from EPREL, modes and the air balance.

Guides

Heat loss calculation: what a room-by-room calculation is and what depends on it

A heat loss calculation gives the power a house needs in the coldest hour, room by room, to EN 12831-1. Worked example: 1,100 ft², 15,651 Btu/h.

Guides

How to design radiant floor heating in HeatAlgo - a step-by-step guide

Radiant floor layout tool and calculator in one: upload a floor plan, draw loops yourself or with Algo AI, connect the manifold and download the PDFs.

Guides

How to send the client form and get complete data - a step-by-step guide

How to send the client form in HeatAlgo, from creating the project to accepting your client's data - step by step, screen by screen, no jargon.

Guides

Algo AI assistant in HeatAlgo: what it does, where to find it and its limits

The Algo AI assistant in HeatAlgo: where to open it, how it reads building plans and reviews a project, its two modes, undo, sources and the monthly limit.

Guides

What water temperature does radiant floor heating need? Btu per square foot by floor covering

Radiant floor heat pump or boiler: at 95 °F supply water and 6-inch spacing a slab gives 13.3 Btu/h·ft² under tile, 12.4 under wood, 11.1 under carpet.

Guides

Radiant floor heating layout: tubing spacing on center, and how long a loop can be

Radiant floor heating layout: the area ÷ spacing rule skips the leaders. At 6 in on center it came up 41.7 ft short on one 138 sq ft room.

Guides

Oversized heat pump: why it short cycles and what that costs you

Heat pump short cycling: why a unit 2x too big for the house starts and stops all season, what that costs in efficiency and wear, and how to check the size.

Guides

Radiant floor heating design guide: what a layout should include and how to check one

Radiant floor heating design guide: check room loads, loop schedule and supply water temperature, with a worked 8-loop example in Btu/h, ft and gpm.

Guides

Retrofitting radiant floor heat in an older house: what to measure before you choose a system

Retrofit radiant floor heating: staple-up, panels on top, a thin slab or grooves in a slab. Measure door, threshold and stair heights and room heat loss first.

Guides

Before you get a radiant floor heating quote: what to measure and what to ask the contractor

Before a radiant floor heating installation quote: 6 things to measure and ask, from room-by-room heat loss to oxygen-barrier PEX and slab insulation.

Answers

What should radiant floor flow meters read? 0.14 to 0.37 gpm per loop on one floor

Radiant floor heating flow rate is not one number. On one example floor at 109/100 °F the loops need 0.14 to 0.37 gpm. Use gpm = Btu/h ÷ (500 × ΔT).

Answers

How much PEX for radiant floor heating in a 1,100 sq ft house? 2,619 ft in the floor, 2,834 ft on the order

How much PEX for radiant floor heating in 1,100 sq ft? 2,619 ft in the floor, 2,834 ft on the order. The area ÷ spacing rule misses the leaders.

Guides

Where to put a radiant floor heating manifold: basement, closet or one per floor?

Where to put a radiant floor heating manifold: one floor, two positions, and 115.5 ft less tubing in the leaders when it moved to the middle of the hall.

Answers

Can radiant floor heat be the only heat source? Yes, but the hardest rooms set the water temperature

Radiant floor heat as the only heat source: at 95 °F supply water the floor covers 3 of 8 rooms, at 100 °F 5, at 104 °F all 8. Room by room.

Answers

Is radiant floor heat enough for a bathroom? The same floor gives a third less at 75 °F

Radiant floor heating in a bathroom: at 95 °F water a slab gives 13.3 Btu/h·ft² in a 68 °F room, only 8.9 in a 75 °F bathroom. The example needs 12.9.

Answers

Does a thicker slab reduce radiant floor output? Concrete over the PEX from 1.2 to 3.1 inches, calculated

At 95 °F water, 6-inch spacing and tile, a radiant slab gives 13.9 Btu/h·ft² with 1.2 in of concrete over the PEX, 13.2 with 1.8 in and 11.7 with 3.1 in.

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