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