Upload
edwina-fowler
View
222
Download
4
Tags:
Embed Size (px)
Citation preview
Lesson 10
How can you reduce radon in a home?
Slide 10-2
Brief overview of radon mitigation
• Mitigation: reducing radon in air or water
• Requires trained, registered radon mitigation specialist– See listing at
www.dph.state.ct.us/BRS /radon/ Pubs/rpplist.pdf
Typical radon mitigation system
Slide 10-3
Mitigation design
EPA usually recommends methods that prevent radon from entering the home– Rather than reduce amount already
present
• Design starts with visual inspection– Identify radon entry paths– Identify relevant construction
features
• May require diagnostic tests
Slide 10-4
Methods for reducing radon in air
Some methods depend on home construction, especially foundation design and materials
Some methods apply to all foundation types
• Sealing foundation openings
• Home/room pressurization
• Heat recovery ventilation (HRV), or air-to-air heat exchange
• Natural ventilation
Slide 10-5
Sealing foundation openings
Method• Seal cracks and other
openings to reduce radon entry
Advantages• Reduces loss of
heated or cooled air• Makes other methods
more effective and cost-effective
Disadvantages• Difficult to identify and
permanently seal all places where radon enters– Some areas are not
accessible– Normal settling
opens new cracks and reopens old ones
Sealing alone does not reduce radon enough
Slide 10-6
Home/room pressurization
Method• Fan blows air
from upstairs or outdoors into lowest living levels
• Increases pressure to reduce radon entry
Disadvantages• Requires doors and
windows on lowest level to be kept closed except for normal entry and exit
• Introduces more outdoor air, so may increase moisture and energy costs
• Effectiveness limited by– Home construction– Climate– Appliances – Resident lifestyle
Use only with other methods if
they do not reduce radon
enough
Slide 10-7
Heat-recovery ventilation (air-to-air heat exchange)
Method• Increases ventilation by
bringing in outdoor air and removing indoor air
• Outgoing indoor air heats or cools incoming air
• Most effective when ventilating a limited space, such as a basement
• Can be used year-round
Advantage• Can improve
overall air quality where there are other indoor pollutants
Disadvantage• Can significantly
increase heating and cooling costs
Slide 10-8
Natural ventilationMethod• Opening windows, doors, and vents on lower levels
increases ventilation• Outdoor air mixes with indoor air, diluting radon • Indoor and outdoor air pressure is equalized
Disadvantages• When openings are closed, radon
returns to higher level in 12 hours• Greatly increases energy costs
because heated and cooled air is lost• May make home uncomfortably hot
or cold• May make home less safe
Use only as a
temporary method
Slide 10-9
Methods forspecific foundation types
Concrete poured at
ground level
Shallow unfinished
space below first floor
Room partly or
completely below ground
Slide 10-10
Basement and slab-on-grade options
Suction prevents radon from entering home
• Draws radon from below home• Vents radon to pipe(s)• Releases radon to air above
home
Types of suction• Subslab
– Active– Passive
• Drain tile• Sump hole• Block wall
Slide 10-11
Active subslab suction(or subslab depressurization)
• Reliable• Effective in reducing high radon
levels• Suction pipes inserted through
slab into soil or crushed rock below
• Vent fan draws up radon gas and releases it outside, above the roof eave
• Works best when air moves easily under slab
Slide 10-12
Subslab suctionPassive
• Similar to active system but• Instead of fan, natural air
pressure differences and air currents draw up radon gas
• Less effective in reducing high radon levels
• Usually used with radon-resistant features in newly built homes
Slide 10-13
Drain tile suction
• Drain tiles or perforated pipe direct water away from foundation
• Works with a partial or complete loop of drain tiles
• Suction pulls radon from soil and vents away from home
Slide 10-14
Sump hole suction
• Used in basement with sump pump designed to remove water
• Sump is capped and continues to operate
• Sump becomes location for radon suction pipe
• Works best when air moves easily to sump from under slab
Slide 10-15
Block wall suction
• Used in basement with hollow block foundation walls
• Requires that major openings be sealed
• Removes radon and depressurizes block wall
• Often used in combination with subslab suction
Slide 10-16
Crawlspace options
• Submembrane suction
• Active depressurization
• Crawlspace ventilation
Slide 10-17
Submembrane suction
Method• Cover earth floor
with high-density plastic sheet
• Vent pipe and fan draw radon from under sheet and vent to outdoors
Advantage• Most effective
method
Slide 10-18
Active depressurization
Method• Fan draws air
from crawlspace
Disadvantages• Less effective than
submembrane suction• Requires special attention to
backdrafts of combustion appliances
• Requires sealing crawlspace from rest of home
• May increase energy costs because heated or cooled air is lost
Slide 10-19
Crawlspace ventilation
Methods• Active: fan blows air
through crawlspace• Passive: vents
circulate air naturally in crawlspace
Disadvantages• Water pipes, sewer
lines, and appliances in crawlspace may need to be insulated against cold
• May increase energy costs
May lower radon by1. Reducing suction on soil2. Diluting radon beneath a home
Slide 10-20
Various foundations mayrequire various methods
Slide 10-21
Questions?
Slide 10-22
Removing radon in water from private wells
Point-of-entry system• Removes radon
before water is distributed
• Treats all water in home
• Types– Granular activated
carbon– Aeration
Point-of-use system• Removes radon
from water at tap• Treats only small
percentage of household water
• Less effective than point-of-entry
Slide 10-23
Granular activated carbon (GAC) system
• Used to treat radon in water levels from 5,000 pCi/L to below 10,000 pCi/L
• Less expensive
• Filters water through carbon bed, which traps radon and radon decay products– Tank may emit some radiation and may
require shielding– Filter must be changed each year
Slide 10-24
Aeration system
• Used to treat radon levels 10,000 pCi/L and above
• More expensive• Mixes water with air
and vents radon outdoors
• System does not become radioactive
• Requires yearly cleaning
Slide 10-25
Summary
• Mitigation should be done by qualified contractor
• Mitigation involves– Visual inspection– Consideration of
home construction– Possibly diagnostic
tests
• General mitigation methods– Sealing foundation
openings– Home/room
pressurization– Heat recovery
ventilation– Natural ventilation
Slide 10-26
Summary
• Methods for slab-on-grade and basement foundations– Subslab suction– Drain tile suction– Sump hole suction– Block wall suction
• Methods for crawlspace foundation– Submembrane
suction– Active
depressurization– Crawlspace
ventilation