Need a mandate for improving day-lit areas, ventilation and heat gain reduction to improve thermal comfort of affordable housing
CSE’s assessment of Telangana's Dignity Housing Scheme says that it meets some of the thermal comfort requirements, but not all
New Delhi, December 26, 2021: When investments in affordable housing are expanding under Central and state government housing schemes, on-ground assessment of emerging building stock in states shows there is still considerable scope of reducing heat gain in buildings, improving ventilation and day-lit areas to improve thermal comfort for all and reduce energy intensity of built structures. This has emerged from the pilot assessment of the affordable housing schemes – the Dignity Housing Scheme – in Telangana, carried out by Centre for Science and Environment (CSE).
This has also shown that as new development is getting pushed beyond the city’s periphery due to the constraint of land availability, provision of services including education, healthcare, transport and decentralised services of sanitation and water in close proximity have to improve. Otherwise, this can reduce liveability and sustained occupancy making investments wasteful.
This new report – Guidelines for Affordable Housing in Telangana -- was released by the Special Chief Secretary, Government of Telangana, Arvind Kumar, in a meeting organised jointly by CSE and Administrative Staff College in Hyderabad. This brought together wide spectrum of target groups including regulators, building industry, architects, academia, civil society actors, among others.
“This assessment has underscored the importance of integrating thermal comfort requirements when real estate recovery is expected to add millions of dwelling units to the formal housing stock in the next three-four years in the country. Otherwise, the new infrastructure can lock in enormous energy and resources guzzling when India has to meet an ambitious target of billion tonne of carbon reduction by 2030 for climate mitigation,” says Anumita Roychowdhury, executive director, research and advocacy at CSE. In fact, India’s Cooling Action Plan (ICAP) has projected the cooling demand to increase 11 times in buildings between 2017-18 and 2037-38.
“This is particularly important in view of the ambition of the ICAP that has set a target of reducing cooling demand by 25-30 per cent and reducing cooling energy requirements by 20-40 per cent by 2037-38 and has asked for setting thermal comfort standard”, says Rajneesh Sareen, programme director, sustainable habitat at CSE.
About the study: CSE has assessed Telangana state government’s 2BHK scheme -- Dignity Housing -- that allots dwelling units to poor households free of cost. This draws support from the central scheme of Pradhan Mantri Awas Yojana (PMAY) and from the state government. State Department of Municipal Administration and Urban Development (MAUD) and Telangana State Housing Corporation Ltd (TSHCL) are implementing the scheme. Greater Hyderabad Municipal Corporation (GHMC) is also at the helm.
This has assessed and simulated the building design, material and layout plan currently being adopted in housing projects to verify adoption and effectiveness of thermal comfort requirements related to ventilation, building orientation, exposure, thermal transmittance properties of materials, shading devices, daylighting approaches among others. These are required under the key regulations of Eco Niwas Samhita 2018, Energy Conservation Building Code for residential buildings (ECBC-R) and National Building Code 2016 (NBC).
This thermal comfort analysis has assessed key parameters including openable window-to-floor area ratio that indicates potential of using natural wind for ventilation in the building. Visible Light Transmittance that indicate potential of using daylight; and residential envelope transmittance value that is a measure of net heat gain rate through the building envelope (walls etc).
This study has also assessed the liveability aspects of the settlements including locational characteristics of sites, layout of building clusters and access to basic services like education, health care and transportation.
This has also simulated and demonstrated how by changing some basic features like building orientation, shading of buildings, materials with lower heat gain, day lighting and ventilation can help to increase thermally comfortable hours for all including low income groups and reduces dependence on energy guzzling cooling devices.
Different building typologies were selected from Telangana’s two climate zones — composite and warm-humid -- D Pochampally, Kollur II (high-rise typology), and Gajwel (ground+1) in Composite climate zone; and YSR Nagar (ground+2) in warm-humid climate zone. The building clusters include Kollur II, D Pochampally, Dundigal, Ambedkar Nagar, Dhupakunta, Gajwal, Mulugu, YSR Nagar, Vandanam, and Chintakunta.
Daylighting and ventilation can be compromised if layout plans of building clusters are not planned well: Existing energy efficiency regulations have laid down minimum threshold for day lit areas and ventilation in buildings. Even if individual buildings meet these requirements the overall cluster plan can impede its effectiveness. It was found that a building block that is compliant with the relevant rules on its own was capable of having 38 per cent daylit area. But in a cluster form of mass housing effectiveness of this could reduce drastically to a mere 7 per cent especially in lower floors. Daylit areas in middle floors could not reach compliance threshold of 25 per cent as per the NBC 2016. Blocks with a central courtyard performed better than linear blocks as there is light ingress from two sides. Lower floors in high rise buildings have poor daylight ingress. Top floors have sufficient daylit area. Thus, building clustering and distance between buildings require attention in the layout.
Inefficient ventilation in the building cluster add to discomfort – needs to improve in pandemic times: Ventilation is influenced by the form, height, distance between buildings, clustering, and placement of blocks on the site. It was found that 60 per cent of buildings in targeted projects were either in wind shadow areas not receiving adequate air exchange while others were too windy. It is therefore necessary to stagger buildings and orient them in a way that they align with favourable wind direction. This can reduce wind shadow area and the tunnel effect.
Most buildings could not comply with the requirements of heat gain through walls as prescribed in Eco Samhita: While several building blocks could adhere to the requirements of window opening and window to wall ratio that are important for day lighting and ventilation, they could not meet the heat gain requirements leading to more thermally uncomfortable hours in the buildings. While the upper limit for heat gain through walls prescribed as per ECBC-R is 15 watts /sq.m. the actual gain could be as high as 22.7 w/sq.m – 1.4 times higher. If not addressed this can increase dependence on energy intense mechanical cooling.
Adoption of energy efficient material need to be combined with fixing of orientation of buildings and shading to reduce heat gain: While current energy efficiency regulations require adoption of building material that allow lower heat ingress through walls, this is not a sufficient condition. This needs to be combined with orientation of the buildings to improve access to sunlight as well as shading and insulation as appropriate. In one building cluster the east-west facing façade had upto 17 per cent extra heat gain compared to the same building facing North-South. When the same building design was simulated by changing the material from concrete blocks to fly ash with lesser heat gain potential, the heat gain dropped by about 40 per cent. Thermal comfort increases even further when shading devices are combined with the walling material in the building envelope. If layouts are constrained or have site limitations insulation may be used in exterior walls. But this can increase cost.
New generation material will require careful approach for improving thermal comfort of buildings: Driven by the need to fast track construction the construction industry is increasingly opting for new generation material like pre-cast concrete wall panel, extruded polysterene core panel etc. Even though these cost more, they are still favoured as these allow to reduce labour cost and time cost. But without insulation and shading they can create heat intensive structures.
Need to make informed choice while selecting material: Telangana is widely using 150 mm concrete blocks in the 2BHK scheme. But materials with better insulation properties such as AAC blocks with 250 mm thick walling can help to increase the annual number of thermally comfortable hours for the building occupiers from193 to 245 hours. It has also been found that a combination of 100 mm AAC along with 150 mm monolithic concrete walling can also increase annual thermal comfort hours by 114 to 158 hours. Monolithic concrete (that can gain excess heat) can be used in the interior load bearing walls while AAC blocks can be used in the exterior wall if the developers are interested in fast paced construction. The analysis shows that a combined strategy of building design, walling material, and appropriate orientation can increase annual thermal comfort hours by upto over 330 hours compared to conventional material and inadequate design.
Access to basic services undermine quality of life and add to cost of living: Geo spatial analysis further shows that most of the new development is happening outside city limit due to the constraint of land availability inside cities. But the structures are coming out without adhering to the basic norms for essential services as per the guidelines. Several sites do not have schools within one kilometre, or health care centres within two km or a bus stop within 400 meters. If this is not addressed as part of the planning and in city master plans this can impede sustained occupancy and increase cost burden for the beneficiaries.
Telangana’s policies are conducive for appropriate urban planning that can contribute to thermal comfort and liveability: Telangana’s 2BHK scheme has provision of mixed-use and high density development for projects in Hyderabad. Telangana Comprehensive Integrated Township Policy provides for walk-to-work concept to save travel time and vehicle kms traveled. This also provides for energy efficiency in buildings. Telangana has also adopted in-situ projects and reservation for EWS and LIG. Moreover, PMAY guidelines have mandated earmarking of locations in master plans. Telangana is updating master plans of major urban centres. This is an opportunity. Most smaller sites are dependent on the centralized infrastructure in the town that constrains availability of basic services in close proximity .For sustained occupancy it is necessary to adhere to the amended Urban and Regional Development Plans Formulation and Implementation (URPDFI) norms among others.
Link fiscal incentives with performance of buildings on thermal comfort: Currently, affordable housing projects enjoy several incentives in terms of FAR/FSI/TDR and tax holidays. It is necessary to link this with the actual performance of buildings in terms of adoption of thermal comfort features, energy consumption, availability of decentralised water conservation, sanitation and recycling treated waste water and waste.
The way forward
As the affordable housing schemes in Telangana have already begun to adopt design features and planning guidelines for improving thermal comfort and liveability of mass housing, this can be leveraged further to scale up the applications by making these requirements mandatory and part of the project approval.
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