Energy eďŹƒcient well-being U N D E R F LO O R H E AT I N G / C O O L I N G I N LO W - E N E R G Y B U I L D I N G S
02 | 2012
Why low energy buildings
The Building sector accounts for 40 % of EU’s energy use and 36 % of the CO2 emissions. More than 90 % of the environmental impact from a building is from its energy use (heating, cooling, ventilation and lighting). Improved energy efficiency is key for both reducing costs, improving competitiveness, securing future supply and for meeting the commitments on climate change stipulated under international agreements. 100 -20 %
-20 %
Energy efficient heating and cooling systems Energy efficient heating and cooling systems are vital for low energy buildings to fulfil the future requirements. New building standards across Europe have demands for higher thermal insulation of the building envelope, better u-values for windows and lower infiltration through the building envelope, all in order to reduce the heat loss. By 2020, building regulations will be adapted to reach nearly zero energy levels. Compared to 2005 building standards, the heat loss will decrease with more than 80 %.
20 % 0 Greenhouse gas levels
Energy consumption
Future residential buildings will have heating peak loads of 20-40 W/m2 and the tight and well insulated building envelope will introduce a need for cooling in the summer period. The cooling peak loads can be significant - up to 40 W/m2.
Renewables in energy mix
140
The 20-20-20 EU Policy by 2020
• • •
20 % cut in EU’s Greenhouse Gas emissions 20 % energy share from renewable sources 20 % increase in energy efficiency
100
kWh/m2 pr year
The European 20-20-20 plan envisages the following goals to be achieved by the year 2020:
120
80
60
40
20
0
2005
2020
Tendency of the energy frame towards 2020
2
U P O N O R · E N E R G Y E F F I C I E N T W E L L- B E I N G
Future proof renewable energy with maximum efficiency Low temperature heating and high temperature cooling Radiant systems, such as underfloor heating and cooling, operate at temperatures close to the indoor environment. Low temperature heating (typically 30-35° C) and high temperature cooling (typically 14-18° C) increases the efficiency of heat sources such as heat pumps and enables the use of renewable energy and sources of free cooling. Only embedded radiant systems, such as underfloor heating and cooling, can operate at optimal temperatures for heat source efficiency and at the same time utilize free cooling sources. Ground-source heating can be incorporated into a radiant system via a ground coupled heat pump. The heat pump performance will significantly increase in comparison to traditional, high-temperature systems and air heating, as the efficiency of a heat pump depends on the supply temperature. A rule of thumb says that lowering the system supply water temperature by 1 ° C will reduce the annual energy consumption by approximately 2 %.
Designed for the future
8 35 °C 7
50 °C 60 °C
6
COP
Even low energy buildings need energy input for maintaining a good indoor environment. The challenge is to provide this energy in the most sustainable way. Studies of low-energy buildings unanimously conclude that optimal comfort and minimum energy consumption is achieved using a combination of water based radiant emitters and ventilation with heat recovery. Forced mechanical ventilation is necessary due to the requirements for building tightness and air change rates. But using the ventilation system as the sole heat emitter leads to inefficiencies. A typical heat recovery system cannot alone provide the heat input required for thermal comfort during peak hours in the winter. Moreover, air heating requires relative high temperature levels, which leads to poor performance of the used energy sources. A radiant heating system gives the best energy efficiency due to its low operating temperature.
9000 8000
kWh/m2 pr year
The lifetime of a building is between 50 and 100 years. Its therefore crucial to install a heating and cooling emitter system that can utilize future energy sources. With an embedded radiant system the building is practically future proof as this would work efficiently with any possible future energy supply system, including individual solutions such as solar and ground energy or possible future district energy solutions. This is valuable for the annual cost of energy as well as for the future property value.
Integrated solutions provides comfort with minimum energy use
7000 6000 5000 4000 3000 2000 1000
5
0
District heating
4
Gas
Air to water heat pump
Ground to water heat pump
3
Radiant floor heating supply 35 °C
2 -5
0
5
10
15
20
°C
Heat pump coefficient of performance (COP) as a function of the primary side inlet temperature (ground temperature) and different emitter system supply water temperatures (35° C , 50 ° C and 60 ° C).
U P O N O R · E N E R G Y E F F I C I E N T W E L L- B E I N G
Air heating supply for heating battery 60 °C
Single family house simulated in Denmark 165 m2 including energy for space heating, domestic hot water and ventilation.
3
Underfloor heating provides superior comfort
An optimal indoor environment requires careful design of the thermal environment, air quality, acoustic conditions and lighting. A well designed underfloor heating system is the first step towards good indoor comfort throughout the year. It provides ideal temperature distribution, eliminates cold draughts and can provide fast reacting room temperature regulation. 18
Optimal indoor temperature Uponor radiant systems are designed to provide optimal room temperatures, which ensure perfect thermal comfort throughout the year. Individual room control secures that different temperatures can be obtained according to user preferences. The optimal temperature according to ISO 7730 is around 21-22°C during the winter and 24-25° C during the summer. Predicted Percentage of Dissatisfied
20
22
24
26
[°C]
Metabolic rate: 1.2
Ideal heating Radiant ceiling heating
Underfloor heating External wall radiator heating
Vertical temperature profile with different emitter systems
Underfloor heating provide superior thermal comfort because the energy exchange takes place as radiation from the floor. The radiant heat exchange results in uniform temperatures within all room surfaces and thus no convection with moving air. The risk of cold thermal draughts and draughts from the mechanical ventilation is practically eliminated.
Self-regulating and fast reaction Basic clothing insulation: 1.0
Basic clothing insulation: 0.5
The indoor temperature in low energy buildings is very sensitive to fast changes in heat gains from for example solar radiation through windows. It is therefore necessary that the heating system can reduce or increase the heating output relatively fast.
Operative Temperature Optimal temperature with winter and summer clothing
Ideal heating distribution A well functioning underfloor heating system results in a vertical temperature profile in the room close to the ideal. This ensures a perfect thermal balance between the human body and its surroundings.
The so-called self-regulating effect of underfloor heating and cooling helps to maintain a stable indoor temperature. The self regulating effect occurs because the thermal mass in the floor will absorb and release energy when the house is exposed to unexpected loads. °C 27
= Floor surface temperature
26
= Room temperature 25
c cooling = 10.5 W/m2
c
24 23 22 21
b a
b heating = 13.9 W/m2
20
a heating = 19.1 W/m2 19
Time (h)
Self-regulating effect where the energy exchange between surface and room it either positive or negative
4
U P O N O R · E N E R G Y E F F I C I E N T W E L L- B E I N G
Optimal room temperature control with a Uponor Control System Meeting the indoor climate needs of the home occupant
Room temperature/set point °C
Providing the right temperature at the right time and place is crucial for individual comfort. People prefer different temperatures in different rooms at different time of the day, e.g. 22 °C in the living room, 19 °C in the bedroom, and 24 °C in the bathroom.
In low energy buildings, there is a high variation in heat loss from room to room depending upon the orientation of the room and the size of the glass area (up to 50 %). With no single room control, the room with the highest heating requirement or set point will influence the other rooms and cause unnecessary use of energy and create overheating in the rooms with smaller heat loads. The saving potential is up to 30 % using individual room control compared with zone control.
25 24 23 22 21 20 19 18 17 16 15
Bedroom
Living room
Home office
Bathroom
Room An example of the typical variation of the preferred room temperatures An example of the typical variation of the heat requirement in a low energy building
Uponor Control System designed for low energy buildings Uponor Control System with DEM technology is designed for low energy buildings and is able to manage heating and cooling with individual room control, supply water and humidity control.
Uponor Controller C-56 Radio and Uponor Interface I-76 together with Uponor Thermostat with display T-75 Radio and Uponor Climate Controller C-46 for supply water control and dew point management.
The DEM technology (Dynamic Energy Management) controls the water flow rate by dynamically evaluating the actual need for certain duty cycles, and release energy using a self-learning algorithm that adapts to the actual room needs. Uponor Control System with DEM technology will provide savings of 5-8 % compared to ordinary on/off room control systems.
U P O N O R · E N E R G Y E F F I C I E N T W E L L- B E I N G
5
The need for Cooling in Low Energy Homes
External Ext tern rnall and d in inter internal ternall heat heat gains gains
Low energy buildings are tight and well insulated. This ensures a low heating bill, but there is a high risk of indoor overheating in the summer. A combined underfloor heating and cooling system can provide sustainable cooling and thus ensure a comfortable indoor environment year round.
to solar radiation, people and electrical equipment also contributes to raising the indoor temperature to unacceptable levels.
Good low energy design includes optimized architecture and building orientation with adequate shading of windows and glass facades. But people’s experiences from living in low energy houses as well as engineering thermal simulations clearly conclude that the need for cooling cannot be eliminated by solar shading alone.
The most efficient shading, with a shading factor of 85%, can reduce the total cooling loads with up to 50% but not eliminate the need for cooling. The tight and well insulated low energy building does not allow the heat to escape and shading and blinds will only partly solve the problem. Active cooling is therefore required, but using traditional “air-conditioning” needs electricity and is therefore not an option within a tight energy frame.
Daylight is needed in the house for peoples well being, but the direct sun radiation through windows causes overheating. A too high indoor temperature does not only occur during summer, but also in the spring and autumn when the sun appears low in the sky. In addition
The solution is to use free cooling from the ground combined with radiant cooling emitter in the floor, wall or ceiling. If an underfloor heating system is installed, this can simply be used for cooling in the summer period by supplying water at ground temperatures. 2%
5%
Heat from air flows 3% 10 %
Heat from occupants (incl. latent) Heat from equipment
13 %
52 %
Heat from walls and floors (structure) Heat from lighting
15 %
Heat from daylight (direct solar) Heat from windows (including absorbed solar) and openings
Cooling load in single family house located in Denmark
6
Distribution of heat gains in single a family house located in Denmark
U P O N O R · E N E R G Y E F F I C I E N T W E L L- B E I N G
Radiant systems as cooling system with ground energy as a “free” cooling source Passive cooling – cooling with almost no operating costs Since a radiant system can cool at relatively high temperatures, it can in fact utilize the typical summer ground temperatures without having the need for a heat pump. The result is explicit “free cooling” as the only operating cost is coming from the pumps circulating the brine/water.
European seasonal energy efficiency ratio (ESEER) 25
20
15
10
5
0
Air to air heat pump
Air to water heat pump
Brine to water heat pump
Passive cooling
ESEER is comparable to a seasonal performance factor in heating season
Heating mode, the free cooling is deactivated
Cooling mode, the free cooling is activated
The figures above show a Uponor heating and cooling system in combination with a ground to water heat pump and a Uponor “free cooling” pump/exchanger group called EPG including the Uponor Climate Controller C-46 that can manage heating and cooling with individual room control, supply water and humidity control.
U P O N O R · E N E R G Y E F F I C I E N T W E L L- B E I N G
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Production: Uponor AB, BG Indoor Climate, Virsbo; Sweden 2012-02-17 EN
Uponor Corporation www.uponor.com
Uponor reserves the right to make changes, without prior notiďŹ cation, to the speciďŹ cation of incorporated components in line with its policy of continuous improvement and development.