Search for: All records

Retrofitting building stock through heating electrification and energy efficiency improvements is essential for achieving carbon neutrality. Understanding the effects of electrification and efficiency retrofits on building-resident satisfaction and adaptive behaviors is important, as these directly impact retrofitting success, adoption rates, energy consumption, and performance. There is a gap in understanding the combined effects of heating electrification and building efficiency retrofits. Using data collected over 2.5 years, we performed integrated qualitative and quantitative analyses to evaluate the combined effects of heat pump electrification and a roof insulation retrofitting in a 10-unit New York City apartment building. Building-resident satisfaction with each strategy was assessed, and impacts on occupant thermal comfort, energy behavior, indoor thermal environment, and energy consumption were analyzed. Despite perceived challenges and resident skepticism, air source heat pumps (ASHPs) provided adequate indoor thermal comfort. ASHPs were preferred over steam boiler heating for controllability, noise reduction, and improved thermal comfort. Unintended benefits included improved aesthetics, reduced real estate needs, and decreased burn potential. With heat pumps, some residents adopted energy-conservative behaviors while others adopted “comfort-taking” behaviors, prioritizing comfort over conservation. The roof insulation retrofit further improved resident thermal comfort and decreased total building heating energy requirements by 25.3–34.2% and heating peak power requirements by 10.7%. The retrofit also improved ASHP efficiency in previously uninsulated spaces, effectively mitigating heat pump undersizing effects. Combined energy retrofitting strategies could play a key role in ensuring thermal comfort and building energy efficiency toward carbon neutrality. 

In nanoparticle-assisted photothermal microscopy, absorption of radiation by a nanoparticle is followed by non-radiative relaxation which leads to changes in the surrounding medium temperature, pressure, and density. Under harmonically modulated irradiation, the finite heat diffusion rate causes a phase delay between the thermal oscillation at a location in the medium relative to that at the nanoparticle surface. The phase delay averaged over the probe laser volume can be measured concomitantly with the amplitude of detected probe power modulation. In this study we show that, in conjunction with the more widespread measurement of the modulation amplitude, the photothermal phase can provide a complementary, sensitive probe of thermally-induced changes in the local medium properties. As proof of principle, we study a widely used, technologically important polymer resist -- polydimethylsiloxane (PDMS). In addition we show how, with the help of simulations, it is possible to extract from phase/amplitude data the temperature-dependent properties of the photoannealed medium.