Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (44 results)

  • Article
LBL Publications (2014)
    Cover page: A Meta-Analysis of Single-Family Deep Energy Retrofit Performance in the U.S.
    • Article
    LBL Publications (2014)
      Cover page: A Meta-Analysis of Single-Family Deep Energy Retrofit Performance in the U.S.
      • Article
      • Peer Reviewed
      Indoor Environmental Quality (IEQ) (2012)

      Today’s high performance green homes are reaching previously unheard of levels of airtightness and are using new materials, technologies and strategies, whose impacts on IAQ cannot be fully determined by past efforts.  This research assessed IAQ in 24 new or deeply retrofitted homes designed to be high performance green buildings in California using pollutant measurements, home inspections, diagnostic testing and occupant surveys.  Measurements included six-day passive samples of nitrogen oxides (NO2 and NOx), formaldehyde (HCHO), acetaldehyde (CH3 CHO) and air exchange rate (AER); time-resolved data loggers were used to measure carbon monoxide (CO), particle counts (PN), temperature (T) and relative humidity (RH), as well as ultrafine particle count (UFP) during stovetop testing. 

      Only 13 of 24 homes provided continuous mechanical ventilation, and no relationship was found between mechanical venting and either AER or pollutant levels, with the exception of particulate, which was actively filtered by 12 of 13 ventilation systems.  Naturally vented homes were much less airtight, on average (6.7 vs. 2.3 ACH50).  Numerous faults were observed in complex mechanical ventilation systems, suggesting need for more rigorous commissioning.  AER did not significantly determine either formaldehyde or particulate levels, but they did for NO2.  Median formaldehyde concentrations in bedrooms and kitchens (17.5 and 20.1 μg/m3) were approximately half those found in conventional new CA homes by previous research (36 μg/m3) (Offermann, 2009).  Source control (engaged in by 22 of 24 households) was most likely responsible for this result.  NO2 concentrations were generally low, with concentrations in gas cooking kitchens 2.4 times higher than electric (13.1 vs. 5.4 ppb).  Three gas cooking homes exceeded the CalEPA annual ambient air standard for NO2.  Those homes that provided active particle filtration had lower indoor particle count levels than unfiltered homes.  UFP emissions were dramatically lower on induction electric cooktops, compared with either gas or resistance electric models.  Kitchen exhaust fan usage rates were low, with occupants believing that everyday cooking was harmless, suggesting a lack of education on IAQ impacts of cooking.  Finally, shortcomings affecting high performance green homes were identified in current U.S. codes and standards.  The results of this research suggest that with better occupant education, careful system design and commissioning, particle filtration and source control, high performance green homes can provide acceptable or enhanced IAQ. 

        Cover page: Indoor Air Quality in 24 California Residences Designed as High Performance Green HomesCreative Commons 'BY-NC-SA' version 3.0 license
        • Article
        LBL Publications (2013)
          Cover page: Deep Energy Retrofits - Eleven California Case Studies
          • Article
          LBL Publications (2015)
          The U.S. DOE Building America program has established a research agenda targeting market-relevant strategies to achieve 40% reductions in existing home energy use by 2030. Deep Energy Retrofits (DERs) are part of the strategy to meet and exceed this goal. DERs are projects that create new, valuable assets from existing residences, by bringing homes into alignment with the expectations of the 21st century. Ideally, high energy using, dated homes that are failing to provide adequate modern services to their owners and occupants (e.g., comfortable temperatures, acceptable humidity, clean, healthy), are transformed through comprehensive upgrades to the building envelope, services and miscellaneous loads into next generation high performance homes. These guidance documents provide information to aid in the broader market adoption of DERs. They are intended for inclusion in the online resource the Building America Solutions Center (BASC). This document is an assemblage of multiple entries in the BASC, each of which addresses a specific aspect of Deep Energy Retrofit best practices for projects targeting at least 50% energy reductions. The contents are based upon a review of actual DERs in the U.S., as well as a mixture of engineering judgment, published guidance from DOE research in technologies and DERs, simulations of cost-optimal DERs, Energy Star and Consortium for Energy Efficiency (CEE) product criteria, and energy codes. These guidance documents include specific recommendations for each Building America climate zone, as well as guidance on more general topics, including: • Lessons learned on U.S. DERs • Guidance for the overall DER process • Controlling costs and increasing cost-effectiveness • Fuel switching, adding energy uses and source energy/carbon emissions considerations • Occupant behavior in planning, design and operations • Over-time or phased approache
            Cover page: Deep Energy Retrofit Guidance for the Building America Solutions Center:
            • Article
            LBL Publications (2020)
            This study performed detailed thermal and moisture measurements in two homes in Fresno and Clovis, California with sealed attics insulated with glass fiber insulation to determine moisture performance in inland California climates. Data were recorded once every minute for more than a year in each home to allow detailed observation of time-varying moisture and thermal conditions. Moisture measurements were taken at multiple locations in each attic and included wood moisture, surface condensation and surface relative humidity. The results showed that there are strong solar-driven diurnal cycles in attic wood and air moisture content, as well as longer-term seasonal and annual variations. Mold growth was observed on the North roof deck in one of the two homes even in this sunny dry climate with attics built in compliance with California building codes that specifically address sealed and insulated attics with vapor- permeable insulation. We investigated moisture stratification in the attic and found that, although there is stratification during sunny daytime hours, this was not when wood moisture content, surface humidity or surface condensation are high. Therefore, other moisture transport mechanisms are acting to increase moisture levels near the roof peak. Our measurements also showed that the attic with the highest measured moisture levels did not have any mold growth, while mold was visually observed in the attic whose measurements indicted little or no concern, indicating that the state-of-the-art in moisture measurement and mold growth prediction in building assemblies may be insufficient.
              Cover page: Measured Moisture Performance of Sealed and Insulated Attics with Permeable Insulation In California Homes
              • Article
              LBL Publications (2015)
              The U.S. DOE Building America program has established a research agenda targeting market-relevant strategies to achieve 40percent reductions in existing home energy use by 2030. Deep Energy Retrofits (DERs) are part of the strategy to meet and exceed this goal. DERs are projects that create new, valuable assets from existing residences, by bringing homes into alignment with the expectations of the 21st century. Ideally, high energy using, dated homes that are failing to provide adequate modern services to their owners and occupants (e.g., comfortable temperatures, acceptable humidity, clean, healthy), are transformed through comprehensive upgrades to the building envelope, services and miscellaneous loads into next generation high performance homes.These guidance documents provide information to aid in the broader market adoption of DERs. They are intended for inclusion in the online resource the Building America Solutions Center (BASC). This document is an assemblage of multiple entries in the BASC, each of which addresses a specific aspect of Deep Energy Retrofit best practices for projects targeting at least 50percent energy reductions. The contents are based upon a review of actual DERs in the U.S., as well as a mixture of engineering judgment, published guidance from DOE research in technologies and DERs, simulations of cost-optimal DERs, Energy Star and Consortium for Energy Efficiency (CEE) product criteria, and energy codes.These guidance documents include specific recommendations for each Building America climate zone, as well as guidance on more general topics, including: Lessons learned on U.S. DERs Guidance for the overall DER process Controlling costs and increasing cost-effectiveness Fuel switching, adding energy uses and source energy/carbon emissions considerations Occupant behavior in planning, design and operationsOver-time or phased approaches
                Cover page: Deep Energy Retrofit Guidance for the Building America Solutions Center
                • Article
                • Peer Reviewed
                LBL Publications (2018)
                  Cover page: Rethinking Occupancy - Based Ventilation Controls
                  • Article
                  LBL Publications (2016)
                  Elevated indoor humidity levels in homes represent a risk to occupant thermal comfort and health, as well as building durability. The improved thermal properties of high performance homes lead to less cooling system run time and associated moisture removal. High performance homes often have elevated indoor humidity, as a result. Current technologies for addressing this high humidity include dehumidifiers, energy recovery ventilators and enhanced cooling strategies. A strategy that has not been assessed to-date is the smart control of ventilation systems to better manage indoor moisture and reduce humidity loads. Such smart controls time-shift ventilation to reduce the duration and number of hours of high indoor humidity, while providing annual pollutant exposure equivalent to a continuously operated fan sized to ASHRAE Standard 62.2-2013. The REGCAP simulation tool was used to assess 13 smart ventilation control strategies. Elevated indoor humidity was mostly problematic only in smaller homes with higher moisture gains. The best controls were able to achieve significant reductions in indoor humidity without excessive energy penalties (e.g., 16% of annual hours reduced below 60% RH in a small Miami home, using 277 kWh annually). They also maintained equivalent air quality to a continuous 62.2-2013 fan. In the cases with highest indoor humidity, smart ventilation controls did not eliminate the need for supplemental dehumidification, with 20 to 25% of annual hours remaining >60% RH.
                    Cover page: Smart Ventilation Control of Indoor humidity in High Performance Homes in Humid U.S. Climates:
                    • Article
                    LBL Publications (2014)
                    Because airtightening is a significant part of Deep Energy Retrofits (DERs), concerns about ventilation and Indoor Air Quality (IAQ) have emerged. To investigate this, ventilation and IAQ were assessed in 17 non-smoking California Deep Energy Retrofit homes. Inspections and surveys were used to assess household activities and ventilation systems. Pollutant sampling performed in 12 homes included six-day passive samples of nitrogen dioxide (NO2), formaldehyde and air exchange rate (AER); time-resolved data loggers were used to measure particle counts. Half of the homes provided continuous mechanical ventilation. Despite these homes being twice as airtight (3.0 and 7.6 ACH50, respectively), their median AER was indistinguishable from naturally vented homes (0.36 versus 0.37 hr--1). Numerous problems were found with ventilation systems; however, pollutant levels did not reach levels of concern in most homes. Ambient NO2 standards were exceeded in some gas cooking homes that used legacy ranges with standing pilots, and in Passive House-style homes without range hoods exhausted to outside. Cooking exhaust systems were installed and used inconsistently. The majority of homes reported using low-emitting materials, and formaldehyde levels were approximately half those in conventional new CA homes (19.7 versus 36 ?g/m3), with emissions rates nearly 40percent less (12.3 versus 20.6 ?g/m2/hr.). Presence of air filtration systems led to lower indoor particle number concentrations (PN>0.5: 8.80E+06 PN/m3 versus 2.99E+06; PN>2.5: 5.46E+0.5 PN/m3 versus 2.59E+05). The results indicate that DERs can provide adequate ventilation and IAQ, and that DERs should prioritize source control, particle filtration and well-designed local exhaust systems, while still providing adequate continuous ventilation.
                      Cover page: Indoor Air Quality and Ventilation in Residential Deep Energy Retrofits
                      Top