Concept 10 by ONEKA: Transparent insulation Cross section figures of the existing wall / the refurbishment concept Market potential and reasoning Application Known problems related to refurbishment method Material layers and thicknesses Description of working methods Existing wall type Refurbishment concept Sustainability aspects Durability Impact on energy demand for heating Impact on energy demand for cooling Impact on daylight Environmental impact Indoor air quality and acoustics Structural stability Fire safety Aesthetic quality Effect on cultural heritage Life cycle cost Need for care and maintenance Disturbance to the tenants and to the site Buildability
Concept number 10 ONEKA Transparent insulation The innovation of this concept combines the properties of good optical transmission with good thermal insulation. Transparent insulation (TIM) improves the thermal performance of the exterior wall not only by reducing the transmission losses but also by enabling solar gains. The system reduces energy demand through better U-values, by acting on the wall or on the windows. It increases solar gains through the wall thus enabling renewable solar energy. Depending on the amount of solar radiation and the external temperature the transmission loss is reduced or the heat transfer is reversed. The transparent insulation acts as heating system. This system is not suitable for climates where cooling is demanded because it increases solar gains through the wall, but it is quite plausible in more temperate areas. Application The concept is suitable for the following application areas: - BUILDING TYPES - single/detached family houses and multi-storey buildings. - CURRENT STRUCTURE OF EXTERNAL WALL - cavity brick walls: - Plaster (15 mm), inner leaf of hollow brick (70 mm), cavity (30-40 mm, insulation in some cases (30 mm), outer leaf of solid or perforated brick (115 mm) - CLIMATIC ZONES Csa - temperature with dry, hot summer Cfb - cold, without dry season and with warm summer Market potential The double skin external wall is the most common façade for residential buildings since 1950 (i.e: Spain). Adding thermal insulation to external wall were not required by Rules and Regulations until 1979, that is why the market potential building stock is the one built before this date. In any case, this refurbishment solution can be equally used for any building up to now. Reasoning This system is eligible for new buildings optimized for solar gains as well as for the improvement and renovation of existing buildings, to provide improved heat insulation, solar gains and comfortable light. There are two variants of Transparent Insulated Solar Walls: 1. Solar Wall as heat storage: Integrated in a façade insulation system it does not only reduce thermal losses by insulation, but heats the building as well by using sun energy. (OPAQUE) 2. Solar Wall as day lighting system: this system saves electrical power and permits daylight without glare. (TRANSLUCENT) There are also different materials of transparent insulation, but honeycomb has larger flexibility for the application, according to its orientation.
1. SOLAR WALL AS HEAT STORAGE TIM combines the properties of good optical transmission (described by the total solar transmittance) and good thermal insulation (describes by the heat loss coefficient of U-value). The principle: Solar rays cross the light permeable Transparent Insulation module and hit the dark massive wall. Here the solar power is converted into heat and stored in the wall, which conducts the heat with a time delay of several hours into the interior. Functional principle of solar wall heating Transparent insulation (TIM) improves the thermal performance of the exterior wall not only by reducing the transmission losses but also by enabling solar gains. The solar radiation on the wall is transmitted through the insulation material and absorbed at the exterior surface of the inner shell of the wall and converted to heat. The insulation material in front ensures that a large part of the gained heat is transferred to the inner shell of the wall. Depending on the amount of solar radiation and the external temperature the transmission loss is reduced or the heat transfer is reversed. The transparent insulation acts as heating system. The inner shell works as a storage system and controls the time delay of the heat transfer from outside to inside (depending on its thermal capacity).
Unnecessary fear of overheating In wintertime, when the sun position is low during the day, the rays penetrate almost completely the transparent insulation structure and reach the wall and heats up the whole skin layer. However, during summer when the sun is high, the energy input is very much reduced due to the solar wall principle. In fact, the honeycomb structure shades themselves for high solar altitude. Active solar protection is just need usually for very large glazed areas or for east or west orientation.
2. SOLAR WALL AS DAY LIGHTING SYSTEM Honeycombs in transparent surface Enhancements of TIM: - Reduces direct daylight glare; homogeneous illumination - Daylight is distributed throughout interior with no glare - There are no hard cast shadows Known problems related to refurbishment method Most common refurbishment problems related to transparent insulation concept: - In most regions shading devices are necessary for summer. Active solar protection is needed usually for very large glazed areas or for east or west oriented walls - High investment costs. - Needs approval by the fire department. - Gains can only be used in suitable building types (evening use). - Production is very limited: it s not yet a regular building product; small market.
Cross section figure of the existing external wall Based on deliverable D 3.1 the envelopes studied in South European Countries are the following: (1930 s-1950 s) (1950 s-1980 s) (1950 s-1980 s) (since 1980 s)
Cross section figure of the refurbishment concept The Transparent Insulation concept, as heat storage, applied to the F3 external wall. The solution is the same to the rest of the cases: F3 Cavity brick wall Transparent Insulation + F3 solution
Summary of the materials and layers thickness Description of the Transparent Insulation Materials 1. Elements that allow a good radiation transmission and have good insulation properties. 2. Optimal solar energy index. 3. Light transmission and transparency. 4. Good insulation characteristics: low thermal conductivity value and reduction of the convection effect. The insulation consists of many transparent tubules side by side. In front of the tubules a translucent covering of the insulation. The rays of the sun cross the transparent insulation reaching the façade and goes through an external insulating layer up to a black absorbing plate in which it is turned into heat. Because of the heat insulation the warmed-up absorbing level does not radiate his warmth outside but towards the rear walls, increasing their temperature. Transparent Insulation applies to refurbishment concept cross section below: Transparent insulation 1. glass 6 mm 2. diffusing cloth 1 mm 3q. spacer and sealant equal to insulation
4. transparent insulation material: small-celled plastic honeycomb and capillary structure 60/120 mm 5. glass 6 mm External wall 1. perforated face brick 115 mm 2. cavity 30/40 mm 3. hollow brick 70 mm 4. cement or cement-lime plaster 15mm Description of working methods 1. Beforehand has to check out the condition of the external layer in every case to make a decision whether we can fasten new layers to the existing walls external layer or first we have to do strengthening or it is better to fasten the connecting anchors to the load bearing layer of the wall. 2. When renovating façade the surface has to be clean and dry. Existing exterior paint and mortar layer is scraped off, it can be made by hand or using mechanical means. Possible surface irregularities and minimum deviations can be removed with rough sand paper attached to a float. 3. Water resistant mortar is applied to the whole façade surface. Primer must be thoroughly dried out (min. 24 hours) before panel application. While drying out, the façade must be protected against strong sunlight, rain and wind. At low temperatures and high humidity, the mortar will take longer to dry. 4. There are two supporting methods for TIM panel application: mechanical supports or glue fixing. - Glue fixing: a glue layer is applied on the external mortar layer for honeycombing capillary structure support. Before applying the first layer of adhesive, all corners of the building have to be smooth and reinforced - Mechanical support: precast Transparent Insulation panels are supported by a metal frame (steel or aluminium) which is fixed to the bearing structure of the existing building. A hole is drilled by a crown drill through which stainless elements are places to support the honeycomb insulation panels. 5. Install panels 6. After that the window sill and reveals has to renew and frames have to seal.
Sealing of window and door frames External sealant Window sill and reveals have to be renovated Window and door frames have to seal with appropriate tape. Intermediate sealant The gap around the frame (window and door jambs) is sealed with elastic polyurethane foam. Sealing should be homogenous and air-tight. Internal sealant The façade refurbishment is an outside intervention, TIM as solar wall heat storage, so its not necessary to act in the interior.
Ventilation upgrades required The method itself does not need ventilation upgrade so there is no influence. Information about the performance values needed in the assessment U-value of the total refurbishmed external wall: U F3+TIM = 0,48 W/m 2 ºC Material Thickness, mm Bulk density [Kg/m 3 ] Porosity [-] Properties Specific Heat. Capacity [J/kgK] TIM panel 60 120 R TIM panel = 1,2 m 2 ºC/mW Air cavity (optional) perforated face brick 20.100 λ dry [W/mk] R TIM air cavity = 0,125 m 2 ºC/mW 115 1020-1000 0,595 10 air cavity 50 R air = 0,18 m 2 ºC/mW hollow brick 70 630-1000 0,182 10 cement lime plaster 15 2100-1000 1,8 10 µ dry [-]
Durability (with reference to required service life) and hygrothermal behaviour (in applied climatic zone) Under normal weather conditions and with correct maintenance, the glass has good durability and in fact it does not have problems of moisture so the service life must be long enough. Transparent Insulation Criteria Description Values Unit Thermal performance Transmission coefficient W/(m2K) Thermal bridge effect - Conclusion Good performance Moisture performance Annual moisture accumulation kg/m2/year Indoor climate Overall conclusion Risk for frost damage T<0 C, RH>95% Risk for mould, corrosion T>0 C, RH>80% Risk for condensation, algae, decay T>0 C, RH>95% Conclusion Lowest indoor surface temperature Conclusion Just sufficient h/year h/year h/year C Very good performance Actions Impact on energy demand for heating Reduces energy demand through better U-values, by acting on the wall or on the windows. Increase solar gains through the wall. Impact on energy demand for cooling This system turns out to be harmful to climates where cooling is demanded because it increases solar gains through the wall.
Impact on renewable energy use potential (using solar panels etc.) No impact Impact on daylight Using TIM as lighting system, daylight is distributed through the interior with no glare. Transparent Insulation with different light scattering qualities and added solar protection ensures that an optimum quality and quantity of light and energy is entering the building. The daylight systems have an excellent thermal resistance and provide a high insulation value. Environmental impact Environmental impact from the wall refurbishment concept depends on energy renovation level, building location, building materials used, and energy source used for heating. Impact parameters which considered were carbon footprint, fossil energy- and non-renewable raw material consumption. LCA is made according to next assumptions: Cities Life span is 20 year, For existing and refurbished wall only impact from heating energy is considered. Concept uses transparent insulation, which environmental impact was not known. U-value for existing wall is 1,16 W/m 2 K, U-value for the transparent insulation with glass layers is 0.58 W/m 2 K For heat flux and energy calculations heating degree days based on +18 o C, have been used (see table below). For impact of heating energy main heating type is used. These presented in table below. HDD, +18 o C Heating energy type kg CO 2 eq/kwh Fossil energy consumption, MJ/kWh Non-renewable rawmaterial consumption, kg/kwh Barcelona 1419 Gas 0.271 3.98 0.088 London 2868 gas 0.271 3.98 0.088
Fossil energy, MJ/wall-m 2 /20 year Carbon footprint, kg CO 2 eq /wall-m 2 /20 year 500 450 400 350 300 250 200 150 100 50 Existing wall Ren.2, transparent insulation (glass capillary layer) 0 CF, material CF heating, Barcelona CF heating, London Figure. Carbon footprint for existing-and refurbished walls. Heating type for both cases is gas. Impact from used materials was not known. 7 000 6 000 5 000 Existing wall 4 000 3 000 2 000 1 000 Ren.2, transparent insulation (glass capillary layer) 0 from material from heating, Barcelona from heating, London Figure. Fossil energy consumption for existing-and refurbished walls. Heating type for both cases is gas. Impact from used materials was not known.
Non renewable raw material, kg/wall-m 2 /20 year 160 140 120 100 80 60 Existing wall Ren.2, transparent insulation (glass, capillary layer) 40 20 0 from material from heating, Barcelona from heating, London Figure. Non renewable raw material consumption for existing-and refurbished walls. Heating type for both cases is gas. Impact from used materials was not known. Indoor air quality and acoustics Generally the indoor air quality will not be affected. However, the sealing of window and door frames guaranties that water, air and humidity are not coming inside. The exterior structure reduces outdoor noise. Structural stability Structural stability should be studied individually on each building. The increase of load on the existing wall is going to be minimal because it is going to be mainly supported by the principal structure of the building. Fire safety According to local regulations, it needs approval by the fire department. The expose face of the panel is glass, which protects the inner insulation material, so it makes no fire risk. Aesthetic quality It is necessary to study carefully the encounter of the external wall with windows, doors, eaves, balconies due to the fact that the thickness of the façade has been increased. It can be solved with additional elements such as rabbet, edging profile. Effect on cultural heritage If used to renovate an external wall currently using the same material as the original then it is acceptable. If the external covers up some different existing material then it is necessary to consult local planning conditions.
This system will always modify the external image of the building Life cycle costs Name: Oneka London SusRef Concept: ETICS applied to solid panel Calculation period: 20 years Cost level: 6/2011 Real change of energy price: + 2 %/a Transparent insulation Basic honeycomb glass capillary layer aerogel Heating energy (kwh/m2/a) 80 36 40 17 ECONOMICAL EFFECTS /m 2 /m 2 /m 2 Basic renovation cost 90 90 90 90 Extra renovation cost 0 25 25 50 Heating cost/20 y 160 72 80 34 Life Cycle Cost 250 187 195 174
Need for care and maintenance Care should be taken during construction to ensure that the transparent insulation panels joins are well fixed to the surface as this will encourage the attachment and avoid water penetration. Disturbance to the tenants and to the site Entire structure of external wall remains, so there should be no physical disturbance to tenants, only noise pollution. Buildability The method is quite new and the technology is still been developing.