Abstract:
This study sought to optimize the envelope thermal design of free-running urban residential
buildings in Malawi. It specifically set out to improve the urban residential buildings’ thermal
comfort and suggest optimal envelope thermal design features for these buildings. The research
study was primarily dependent on computer simulations in EnergyPlus to replicate the typical
Malawian urban residential building’s thermal behaviour and then study the impacts of various
envelope configurations on the thermal comfort conditions registered in the building. The simulation
model was experimentally validated to check its appropriateness to the climatic design conditions
prevalent in Malawi and out of the three major cities that were considered, the model was found
to be appropriate for use in the two cities of Mzuzu and Lilongwe leaving out the city of Blantyre.
The optimization methodology that was employed involved the use of orthogonal arrays, statistical
analyses and the listing method. It was found that the optimal envelope thermal design, which
registered up to 18% lower discomfort hours than that of the typical urban residential building,
consists of a 50 mm concrete floor slab, 230 mm burnt brick walls with an external layer of 19 mm
EPS, tiled roof with an internal layer of sarking and 50 mm EPS, double Low-E Glazing with a
transparency ratio of 45% and 0.2408 m2 of adaptable operational surface area for the air bricks.
Out of all the envelope features that were studied, air infiltration registered the most significant
contribution towards the ultimate residential building thermal performance. It was demonstrated
that controlled air infiltration through the use of operable air bricks whose operational surface area is
adaptable can be very effective in enhancing the building’s comfort levels. It was further observed
that excessive insulation of the building envelope generally has a detrimental effect on the indoor
space thermal comfort levels.
