Air Date: 7-22-2016| Episode: 423
This week we go back to the archives and replay a favorite from 1-15-16 with Max Sherman, PhD. Max is a Senior Scientist at the Lawrence Berkeley National Laboratory with over 30 years of experience in building physics…
This week we go back to the archives and replay a favorite from 1-15-16 with Max Sherman, PhD. Max is a Senior Scientist at the Lawrence Berkeley National Laboratory with over 30 years of experience in building physics. He has a Ph.D. in Physics from Berkeley and is an international expert in air leakage, HVAC, indoor air quality, infiltration, moisture, energy efficiency, and related topics. He is a well-regarded member of ASHRAE having served on the Board of Directors and many technical positions and is currently a Distinguished Lecturer; he is a recipient of ASHRAE’s Exceptional Service Award and ASHRAE’s highest technical award as a Holladay Distinguished Fellow. He has also been elected a Fellow of the International Society of Indoor Air Quality and Climate (ISIAQ). He represents the United States on International Energy Agency tasks such as the Air Infiltration and Ventilation Center. He serves on national and international committees and editorial boards and does outside consulting. LEARN MORE this week on IAQ Radio!
- As a kid, Max knew one day he would be a scientist. At Berkeley he had a double major, chemistry and physics. Physics is the most fundamental science and is the most useful for problem solving. He became interested in IAQ when his research adviser told him that “engineers messed up energy efficiency and scientists will need to fix it.” He went directly from U.C. Berkeley to Laurence Berkeley National Lab.
- Physics and IAQ, Physics is the most fundamental of the sciences it helps with learning to approach problems when you do not understand the answer.
- What are the issues, what research is important, what guidelines are needed, what contaminates matter, when modeling is useful and the fundamentals of how to do?
- Ductwork tightness late 1980’s. Develop of blower door technology allowed building tightness to be quantified. 1/3 of the air leakage may be from the ductwork. Losing air out of results in a greater loss of energy.
- In the early 90s 20%-40% of a typical homes energy is wasted by duct leakage, eliminating duct leakage is the best home energy efficiency improvement method.
- Some attics in southern climates can heat up to 160°-180°F, when there is ductwork leakage in these attics the indoor temperature of the home may actually increase when the AC is turned on.
- Where ducts leak matters! Common leakage area in Sunbelt is outside which is worst case for energy. Common in attics for instance.
- With duct leaks in basements we may get some of the air back.
- What is in the air we breathe? Nitrogen, O², moisture and trace amounts of 1000’s of chemicals. The trick to IAQ is to know what things matter and what things to control AKA “contaminates of concern. Particulate is the biggest concern, O³ and formaldehyde are concerns. Acrolein (a severe irritant) was used in WW1 as a weapon. Acrolein is banned from use in warfare. Acrolein is naturally occurs in the incomplete combustion of fossil fuels. Acrolein is an aldehyde that is an irritant and over time a carcinogen.
- Acrolein was used in World War I as a type of gas warfare. It was not banned because its naturally occurring.
- There are low levels in houses comparably speaking but it can still be an irritant and potential carcinogen.
- Ventilation requirements should be based on contaminates. Dilution ventilation is the strategy of last resort. Start with not emitting things in the first place, then air cleaning which is pretty easy for particulates. LBL research shows that particulates have the most health effects.
- Source control eliminate emissions. Combustion sources should be vented. Unvented combustion sources should have exhaust fans & hoods.
- Particulate is the easiest contaminate to remove. Particulate matter <2.5 has greatest health impact on building occupants. Removal of VOCs and air-cleaning is more complicated and costly to perform.
- ASHRAE’s 62.2 ventilation standard was first released in 2003. The ventilation standard was needed because houses were tighter. The standard requires that exhaust fans and range hoods be vented to the outside. A future change in the document provides for particle filtration as a means for reducing ventilation rate. Maine was the first state to adopt 62.2. California is the biggest adopter. Washington and Maine have own standards. The Federal Winterization Program uses 62.2. The standard is a political issue at International Energy Conservation Code®.
- Max, envisions performance based specifications for dealing with VOCs once reasonably priced sensor technology becomes widely available.
- “People are people and contaminates are contaminates” so the need to ventilate doesn’t vary. General residential ventilation is variable due to geographic region, climate, age of home, local traditions, etc. In humid climates de-humidification may be required.
- As homes age building leakage increases. Gaskets, caulking and seals fail. Buildings wiggle and move. Ventilation isn’t difficult in new construction. Running master bedroom bathroom fan 24/7 usually meets 62.2.
- Energy recovery ventilators are an option. Institutional barriers to ventilation exist.
- Should occupants have control over ventilation? Occupants cannot readily sense the impact of small particles and VOCs so ventilation is a must. Occupants should have the ability to go above minimum ventilation rates.
- Has done developmental work on the concept of Residential Integrated Energy Controller that changes the speed of ventilation systems in real time. “Smart Ventilation” adapts and adjusts to external conditions and more time periods when energy is more affordable.
- Range Hoods. The number of range hoods sold is quantifiable; the type of equipment sold is not. Currently no standards or test methods exist for evaluating range hoods. Small scale field testing has shown some have capture efficiency in the 50%-80% range. Re-circulating hoods with filters provide little benefit. Outdoor exhaust is superior. Cooking creates volatile organic compound particles, secondary and tertiary by products. Hot plumes rise so physics work against down draft kitchen exhausts. Some down draft exhausts compensate by having significantly higher airflow rates.
- The largest single thing ASHRAE 62.2 did is require kitchens exhaust to the outdoors.
- Predicts 62.2 will allow more flexibility in future for particle and VOC filtration vs dilution.
- Hoping that the direction in the future will be toward specifying a mix of controls, a more performance based standard.
- The need for ventilation does not vary but the concerns people have to vary. For instance in cold climates ventilation cost money in humid climates moisture.
- As homes age unintended ventilation (airtightness) leakage goes up. Leakage rates vary a lot. They looked at homes 5-10 years later and they found they do get leakier as they age. This was a small study and he is not confident about the why’s.
- Getting ventilation in new homes is easy it becomes a challenge in some existing homes.
- When asked about occupant control over ventilation. OK to give control to go beyond the minimums. Humans are not good sensors about health impacts of air. Minimum rate is something occupants should not have to worry about.
- Airtightness in buildings. We have the technology and know how now to measure and quantify airtightness. We know what works and what doesn’t. Airtightness isn’t a challenge in new construction; airtightness is a challenge in retrofits. Moisture buildup may occur in tight buildings that are under ventilated. Great Return on Investment, one man day of effort (sealing, caulking) = 25% reduction in air leakage.
- Emerging issues: range hoods, acrolein, new products resulting in new contaminates, chronic and acute exposure issues, Health Standard for indoor Air. High excursions of O³ and particulate take a toll on those most vulnerable.
- The philosophical question of “how should we deal with IAQ? Objective quantification and metrics.
- 62.2 is mostly dealing with chronic exposure, studying or dealing with short term acute exposure is harder.