Radon and indoor air quality before and after energy retrofits

Indoor air quality studies of weatherized residential buildings have shown that some pollutant levels increase, while others decrease. A study by Noris et al. (2013) conducted energy retrofits on 16 low-income multifamily apartments that were designed to save energy and improve IEQ. Particulate levels, CO2, and volatile organic compounds (VOCs) generally improved whereas formaldehyde (HCHO) and nitrogen dioxide (NO2) varied by building. Larger decreases in indoor sourced pollutants were realized with larger increases in ventilation rate and IEQ improved more in buildings with added mechanical ventilation (excluding particles).

The picture is similar for indoor radon. The main factors that drive radon levels in homes are radon concentrations in the soil gas around the home (high in Colorado); the pressure difference between the inside of the home and the soil; the infiltration rate of the home; the moisture content of the soil; and the number and size of entry points into the home. A 1994 study by the EPA showed inconsistent results between radon and air tightness (EPA 1994). Research conducted by Oak Ridge National Laboratory (ORNL) on this topic (Pigg et al. 2014) showed that statistically significant net increases in radon levels occurred in weatherized homes, even though the increase was modest. For example, the average radon levels pre-weatherization in EPA zone 1 (high) was 2.4 pCi/l (285 study sites) in the treatment group and 2.7 pCi/l in the control group (162 study sites). After weatherization the treatment group went up by 0.29 pCi/l and the control group went down by 0.5 pCi/L. Note that the changes in radon levels were related to outdoor temperature. This study is currently being repeated controlling for geographical location and season, and using different radon measurement methods. The best recommendation is to test after weatherization has been completed and if the levels are too high, then it can be mitigated with pressure management and venting. Radon abatement is unfortunately not currently allowable under the Weatherization Assistance Program.

The objective of this study is to assess the indoor environmental quality (IEQ) in low-income homes before and after receiving weatherization assistance.

Our hypotheses are as follows:

  1. Weatherization activities will not significantly impact the radon levels within the home, but the levels will be high both before and after and will need remediation;
  2. The mold and moisture problems within the home will be improved upon weatherization;
  3. The home will be more air tight after weatherization;
  4. And indoor concentrations of fine particulate matter will remain the same after weatherization but will be elevated if there is overcrowding in the home.

Results and Discussion

This project provided valuable information about the IEQ in low-income weatherized homes in Colorado Springs, Colorado. Unique to this study was the assessment of mold and moisture, radon, and PM2.5 for 15 low-income pre- and post-weatherized homes. Additionally, if a home had high radon levels, the residents were referred to CDPHE’s low income radon mitigation assistance program.

Figure 1 shows a summary of results of the radon tests performed with Air Chek Charcoal Activated Radon Test Kits. The average value of radon recorded was 3.8 pCi/L and the standard deviation was 2.6 pCi/L. Four of the seven homes tested thus far had acceptable radon levels. Of the three homes that were tested both pre- and post-weatherization, all three showed a decrease in radon level.

radon

Figure 1. Radon test results

The PM2.5 data collected closely resembled the example shown in Figure 2, with significant spikes that likely were caused by cooking. The average level of PM2.5 recorded in each home is shown in Figure 3. The PM2.5 levels in most homes averaged around the maximum recommended value of 35 µg/m3.  Post-weatherization results showed that the average PM2.5 increased slightly. This is likely because the homes are more air-tight after weatherization so fine particles generated in the home will not dissipate as quickly. The best solution is to increase ventilation during a cooking event.

PMtime

Figure 2. PM2.5 concentrations as a function of time. Spikes indicate cooking events.

The average TVOC recorded varied significantly as can be seen in Figure 4. As with PM2.5, the average value increased after weatherization.

PMaverage

Figure 3. Average PM2.5

From the NIOSH Mold and Dampness Assessment Tool, we assessed mold and moisture problems and used this tool again during our post-weatherization visits to determine if identified problems improved. In many cases these conditions remained the same but in some cases there was improvement. One example is a home in which we recorded window stains during the first visit but not on the second visit.

TVOC

Figure 4. TVOC results

Regarding our hypotheses, we can preliminarily conclude based on the data collected to date:

  1. Weatherization activities will not significantly impact the radon levels within the home, but the levels will be high both before and after and will need remediation;

The radon levels in the ERC recruited homes are not significantly elevated. Three of the 7 homes tested to date had levels between 4 and 8 pCi/L. the other four homes had levels below 4 pCi/L. When the weatherization was complete, the 2nd round of testing showed the radon level decreased.

  1. The mold and moisture problems within the home will be improved upon weatherization;

In most cases, the mold and moisture problems were improved upon weatherization.

  1. The home will be more air tight after weatherization;

We do not have the blower door data at this time to validate that the homes became tighter after weatherization, but we think that this is the case due to elevated pollutant levels after weatherization.

  1. And indoor concentrations of fine particulate matter will remain the same after weatherization but will be elevated if there is overcrowding in the home.

Both TVOC and fine particulate matter levels increased upon weatherization possibly due to tightening of the home without added exhaust in the kitchen.

References

EPA (1994). Assessment of the effects of weatherization on residential radon levels.  https://cfpub.epa.gov/si/si_public_record_Report.cfm?dirEntryID=126455, accessed Aug 2016.

Noris, F, et al. (2013). Indoor environmental quality benefits of apartment energy retrofits. Build Environ 68:170–178. doi:10.1016/j.buildenv.2013.07.003

 

Pigg, S., Cautley, D., Francisco, P. W., Hawkins, B., & Brennan, T. (2014). Weatherization And Indoor Air Quality: Measured Impacts In Single-Family Homes Under The Weatherization Assistance Program. (No. ORNL/TM-2014/170). weatherization.ornl.gov. Oak Ridge, TN.

 

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