Danfoss Planning Underfloor Heat Compendium

MAKING MODERN LIVING POSSIBLE

Planning Underfloor Heat

Danfoss Heating Solutions

Handbook

Handbook	Planning Underfloor Heat

Planning criteria	Essential requirements for all calculations:
	• Detailed plan of building, construction of outer
	walls, and size and type of windows.
	These data are essential for calculation of the
	heating load in accordance with EN 12831.
	• Information on the type of flooring and its
	thermal resistance Rλ,B , since the heat output is
	dependentonthefloorconstruction,particularly
	that over screed (in accordance with EN 1264 a
	thermal resistance of Rλ,B = 0.1 m2 K/W Rλ,B	for
	living rooms is specified, in bathrooms Rλ,B	= 0.0
	m2 K/W. Other values up to a maximum of 0.15

m2 K/W are to be separately agreed.) Rλ,B = 0.0 m2 K/W.

• Building plans, building drawings and all room data have to be shown. After the calculations, the pipe layout and data are included in the building plan.

• Danfoss forms for calculations.

Changes in building methods over the last few decades have brought about lower requirements for heating homes, so that Danfoss underfloor heatingcanmeetrespectiveheatingrequirements for even physiologically acceptable surface temperatures. In some rooms, such as bathrooms, additional heating may be necessary, as areas under bath and shower cannot be heated and

a higher temperature is required (24° C instead of 20° C). In such rooms the underfloor heating maintainsthetemperatureinthefloorwhileother heat comes from sources such as wall heating, heated towel rails, etc.

Standards for	Thefollowingstandardshavetobeobservedwhen		EN 13813	Screed Material and Floor Screeds
underfloor heating	planning and installing floor heating:
				Local building regulations.
	EN 1991	Action on structures
				Professional information on interface
	EN1264	Underfloor Heating, Systems and		co-ordinationwhenplanningheated
		Components		underfloorconstructions(ref:BVF).
	DIN 4109	Sound Insulation in the Building	EN 1264 is crucial for the construction of under-
		Industry	floor heating.With the inclusion of EN 13813
			‘Screed Material and Floor Screeds’ three Basic
	ISO EN 140-8 Measurement of sound insulation		Danfoss constructions are possible.
		in buildings and building elements

Estimated pre-calculations

The output tables of Danfoss SpeedUp and Basic heating systems show output values for various room temperatures as well as the temperatures of the central heating water in relation to different floor finishes.These tables give calculations of the mean central heating water temperature with which to run the underfloor heating in order to achieve the desired output.

The required excess heat source temperature determines the supply temperature which is describedinmoredetailinthechapter‘Calculating the supplyTemperature’.The heat flow densities are distributed evenly over the edge and comfort zones.The main central heating water temperature is determined by the type of installation (see output tables).

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29° C

35° C

ti + 9° C = 33° C

Handbook	Planning Underfloor Heat

Standard heating load of an underfloor heated room

When making calculations for Danfoss underfloor heating the standard heat load QN,f of the room is essential. For underfloor heating in multi-storey buildings the heat gain of the shared floor can be included into the calculations if there are no restrictions on the work.

The heat output QH is generally calculated from the standard heat load of an underfloor heated room QH,f plus an extra calculation allowance in accordance with EN 4701 Part 3.

QN,f: Standard heating load of an underfloor

heated room [W]

QH: Heat output calculation

If the heating system, such as an underfloor system, can raise the heat output by raising the heat source temperature the extra allowance is is zero.Thus the calculated temperature output equals the standard heat load of an underfloor heated room.

QH = (1 + x)* QN,f

Thermal insulation to avoid downward heat loss

It is important to consider the thermal resistance of the insulation below the underfloor heating so that the heat of the underfloor heating radiates mainly upwards.

In accordance with EN 1264, Part 4 there are three different kinds of floor/storey constructions and various minimum heat resistances.

The heat resistance Rλ.ins with a single insulation layer is calculated as follows:

Rλ,ins	=	Sins
		λins

			with:
	Thermal Insulation	R Ins, min
			Sins: effective insulation thickness [m]
	A above rooms with similar use	0.75 m2 K / W
			λins: thermal conductivity [W/m K]
	B above rooms with different	1.25 m2 K / W
	use*, unheated rooms (e.g.
	cellar) and on ground floor
	C above external air (-15°C) (e.g.	2.00 m2 K / W
	garages, passage ways)

* e.g. rooms above commercially used premises

Maximum surface temperature ΘFmax

In accordance with EN 1264 maximum surface temperatures for phsysiological reasons are set as follows:

Comfort zone:

Edge zone:

Bathrooms:

Standard room temperatures of 20 or 24° C in bathrooms result in a difference in surface

temperature and room temperature of 9K (in comfort zones and bathrooms) or 15K (in edge zones). Limiting the surface temperature has the effect of limiting the heat output of the underfloorheating.Itis animportantfactorwhen deciding whether to choose additional heating. However, with modern insulation the heat output in underfloor heating is sufficient in 99 of 100 cases.

Fluctuation in temperature (W)

The position of the heating pipe can further influence the output. Depending on the position, varying surface temperatures can occur. Output is higher above the pipes than in between. The difference between the maximum and minimum surface temperatures is called fluctuation (W).

W = θF max - θF min

Larger distances between pipes cause larger fluctuation.Lowerlyingpipesslowdowntheheating systembutthe‘longway’tothesurfacedistributes the temperature evenly, the fluctuation remains small.Sincethemaximumfloortemperaturemust notbeexceeded,largerfluctuationcausesgreater lossinoutputthanasmallerfluctuation.Inthefirst

case,averagefloortemperatureissignificantlylower than the maximum permitted temperature.

max 29°C

W

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