Protective helmets used by fire-fighters must be designed to minimize the amount of heat transferred to the users head while providing durability, comfort, and affordable costs. This thesis highlights the evaluation of new helmet technology specifically tailored to high radiant heat environments to advance the state-of-the-art in head protection for this application. The research focused on the assessment of the outer shells of helmets and the properties of the surfaces. The development included the evaluation of radiation heat transfer, in a laboratory environment, to various helmet shell surface constructions. Industry standards were considered, and critiqued. Experiments were designed to isolate critical design variables for measurement and evaluation. Custom, purpose-built laboratory apparatus for testing helmets were designed, explained and utilized in the testing of specimens. Additionally, market demands for firefighting helmets were explored. Helmet durability was specifically addressed with abrasion criteria established and the reflectivity effects of the abraded surfaces evaluated. Resulting from this study, new surface technologies were identified for possible development in future helmet designs. Various surface materials, finishes, and coatings were compared and contrasted to current industry state-of-the-art equipment. The knowledge discovered further advanced modern head protection science in aim of increased safety and performance of fire-fighting personnel.

Modern firefighter protective equipment is excellent at protecting firefighters from surrounding heat, but how effective is at deflecting incoming radiant heat, and would the use of more reflective textiles, be able to further increase the equipment’s protective properties? This study aims to understand the different properties that reflective materials, compared to standard firefighter outer layers, have against radiative heat flux. The textiles of firefighter turnout gear and the reflective textiles used in the smelting industry have been examined when exposed to varying levels of radiant heat in a cone calorimeter. The materials were examined before and after a layer of soot was applied to them, to understand their capabilities if used in a soot-rich environment. The change in material emissivity, when soot was applied, could then be calculated for each material. The heat reducing properties of the sooted and non sooted materials emissivities were tested, using computer simulations of a firefighter’s full turnout gear. First the radiative and convective heat fluxes were compared within a computational fluid dynamics software called FDS, second the skin level temperature was calculated using VGP, a finite element software that accounts for heat flow further into the skin and body.  During the experiment it was found that the emissivity of the reflective material even after soot application, performed better than that of the standard firefighter gear. In the simulations, the sooted reflective material emissivity would reduce the total heat flux to the firefighter with an average of 19% compared to the sooted standard turnout gear. Using the temperature of 44 °C as the limit for human skin damage, the use of a reflective emissivity would allow a 19% longer exposure to the same incident heat before possible skin damage would occur. Reducing the emissivity of current turnout gear would prove valuable as a method of reducing heat accumulation in a firefighter, especially at key areas more susceptible to the radiative heat flux from smoke-layers and radiative flames. This would in turn provide safer work environments for structural firefighting by reducing heat stress during active operations.

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<p dir="ltr">In U.S. residential buildings, space heating makes up about 43% of total energy use, with natural gas fulfilling 45% of this demand. As climate change concerns escalate, moving away from fossil fuel heating systems to more sustainable options are essential, especially in cold climates where heating needs are significant. Air-source heat pumps are a promising alternative, but their capacity and efficiency decrease as outdoor temperatures drop, impacting comfort due to lower supply temperatures (e.g., 32°C/90°F). This can lead to potential discomfort, as such temperatures feel cooler than skin temperature. Additionally, defrosting cycles pull heat from indoor spaces to clear outdoor coils. Conversely, gas furnaces provide steady heat at higher temperatures (over 49°C/120°F) without defrosting issues. Research shows that discomfort prompts occupants to raise thermostat setpoints and increase energy use.This study aims to investigate the influence of operational characteristics of various comfort delivery systems in cold weather on occupants' thermostat adjustment behaviors, identify the limitations of current heat pump systems, and develop a novel wall-embedded micro heat pump (WEMHP) radiant heating system that enhances comfort and reduces energy consumption, supporting the electrification of residential buildings. To achieve this goal, the research focuses on the following specific objectives: 1) develop a controlled laboratory testbed to emulate different thermal comfort delivery systems, including convective air and radiant systems; 2) investigate occupant setpoint preferences and thermostat adjustment behaviors under different operational modes using a residential community testbed; 3) study occupant thermostat adjustment behaviors for different types of heat pump systems through laboratory experiments; 4) develop and evaluate a novel wall-embedded micro heat pump for radiant heating in buildings; 5) design and test a prototype of the wall-embedded micro heat pump as a proof-of-concept demonstration.</p><p dir="ltr">This study first introduces the Human Building Interaction Laboratory (HBIL), a new facility with a modular design that includes reconfigurable thermally active panels for walls, floors, and ceilings. Each panel’s surface temperature can be independently controlled via a hot and cold water hydronic system, allowing the simulation of various climate zones, building conditions, and different heating/cooling systems. This setup facilitates research on localized comfort delivery, occupant comfort control, active building materials, and more.</p><p dir="ltr">Subsequently, a residential community test-bed was established within a newly built residential community in Indianapolis. A study was conducted in 30 homes to collect data on occupants' thermostat adjustments under two different operation modes: 1) a baseline mode featuring a heat pump paired with an auxiliary heater controlled by default thermostat heuristic rules, and 2) a comparison mode where the auxiliary heater was activated to provide the majority of heating. The findings showed that 8 out of 13 units preferred lower setpoints in the comparison mode, where higher supply air temperatures were utilized. Four distinct setpoint-increasing behaviors were identified, contributing to the observed setpoint differences between the two modes. Notably, two of these behaviors were closely linked to the operational characteristics of heat pumps in cold weather, specifically cases of insufficient and sufficient HP capacity.</p><p dir="ltr">To further explore the differences in setpoint preferences and the motivations behind setpoint adjustments, two scenarios were designed, and 32 experiments with human test-subjects were conducted in a controlled laboratory (Human Building Interaction Laboratory). The first case, with a single-stage heat pump and auxiliary heater, replicated the operational characteristics observed in the field study. The second case, using a variable-speed heat pump with enhanced comfort features, aimed to investigate participants' comfort preferences and provide insights for future heat pump design improvements. According to the thermal comfort survey results, 19 out of 32 participants increased their setpoints in the single-stage heat pump case, even though the heat pump had sufficient capacity to warm the indoor space. Cold air movement and indoor temperature fluctuations due to the heat pump cycling on/off were the main reasons participants reported increasing their setpoints in this case. In contrast, participants felt more comfortable with the variable-speed heat pump in the laboratory study, attributing their comfort to stable indoor temperatures and the absence of cold air movement.</p><p dir="ltr">Finally, a novel wall-embedded micro heat pump (WEMHP) was developed as a new distributed comfort delivery approach with several distinct advantages compared to alternatives: (1) A WEMHP eliminates the need for a secondary water loop and does not require separate indoor and outdoor units. Instead, a WEMHP unit operating in heating mode directly absorbs heat through an embedded heat exchanger (evaporator) at the outside wall surface and then conditions the indoor space using an embedded heat exchanger (condenser) at the indoor surface. (2) This packaged solution eliminates the need for extensive HVAC installation and on-site refrigerant charging. (3) The interior surface temperature of the exterior wall section empowered by the micro heat pump is independently controlled, allowing for distributed space conditioning and delivery of radiant heating to meet diverse occupant needs in different zones. The system performance was studied thoroughly based on energy simulation and experimental comfort study. Moreover, a prototype WEMHP was designed, assembled, and tested in a laboratory environment as a proof-of-concept demonstration. The test results demonstrated that the heating capacity under condition H1 reached around 190 W at a compressor speed of 4000 RPM with a COP of 1.67. Additionally, the system exhibited a fast thermal response, with a time constant τ₆₃ (the time it takes for the surface temperature to reach 63% of the difference between its final and initial values) of less than 0.5 hours and a τ₉₅of approximately 1.5 hours.</p>