Ventilation and Moisture Control in Spray Foam Insulation.
spray foam insulation
Ventilation and Moisture Control in Spray Foam Insulation? Spray foam insulation has been
increasing in popularity over the last
several years due to :
• Becoming more affordable.
• Significant long-term energy savings.
SFINJ Master Installer Study Guide
Ventilation and Moisture Control in Spray Foam Insulation.
Indoor air quality is increasingly important because it directly affects the health and comfort of building occupants.
The three key components that impact air quality are:
• Airborne materials (pollutants), often referred to as the quality of the air
• Moisture level (contributing to humidity, condensation, and mold)
• Ventilation/air exchanges (replenishing oxygen levels and diluting air pollutants impacting air changes and safety).
• A key means of controlling indoor air quality is to control the air exchange rate/ventilation.
• ASHRAE 62.2 is the national MINIMUM ventilation standard of design for all homes and up to three-story multifamily buildings.
Inadequate ventilation can increase indoor pollutant levels by not bringing in enough outdoor air to dilute
emissions from indoor sources and not carrying indoor air pollutants out of the home can lead to health problems.
Therefore providing mechanical fresh air ventilation is especially important in spray foam houses.
Mechanical ventilation systems allow a constant flow of outside air into the home and provide filtration, dehumidification, and conditioning of the incoming outdoor air.
Build it Tight and Ventilate Right.
Build it Tight and Ventilate Right… Design and recommend ventilation for homes tightened with SFINJ. The SFINJ contractor must always install a proper ventilation system in a home air-tightened with SFINJ, or assure that the home owner’s or general contractor’s HVAC contractor has provided adequate ventilation.”
While most spray foam homes are required to have some form of mechanical ventilation (ASHRAE 62.2 Standard is recommended), there are many questions on
how best to provide it:
• Exhaust
• Supply
• Balanced
Exhaust Ventilation
Exhaust ventilation systems pull stale air out of the home creating a negative pressure in the house and relying on make-up air leakage through the structure.
• In-line duct fans
• Bathroom fans
• Kitchen hoods
Pros – Positive
• Generally easiest to install
• Can be used with any heating system
• Lowest electrical energy cost
• Simplest to understand
• Simplest to maintain
• Simplest installed system testing
Cons
• Puts house under negative pressure (Not good for AC climates)
• Unknown sources of makeup air
• Highest conditioned air cost
• Ventilation air is not distributed
Supply ventilation
Supply ventilation systems push air into the home, creating a slight positive pressure and providing make-up air for kitchen hoods and bathroom fans.
• Controlled mechanical damper
• Whole house ventilating dehumidifier
Supply Ventilation – Controlled Dampers
Pros – Positive
• Low initial investment
• Can bring in the required amount of fresh air
Cons
• Uses the biggest motor in the home to move a small amount of air. The HVAC system typically moves 1000 to 2000 cubic feet per minute (cfm) of air, but most homes need only 50 to 100 cfm for
ventilation.
• Brings in outside air at times when the heating or cooling system isn’t operating – unconditioned air.
Supply Ventilation – Whole House Ventilating Dehumidifier
Pros – Positive
• Utilizes dedicated fan to operate
• Brings in fresh air and conditions it
• Filters the air
Cons
• Initial investment
• Footprint of the units
Balanced Ventilation
Balanced ventilation systems use one fan to bring fresh air into the home and another to exhaust an equal amount of the outdoors.
• Energy Recovery Ventilator
• Heat Recovery Ventilator
ERVs and HRVs are balanced ventilation systems initially developed for northern climates. They bring air into the home and blow an equal amount out of it. The ERV/HRV core transfers heat and, in an ERV, moisture (energy) between the two air streams.
Balanced Ventilation – ERV & HRV
Pros – Positive
Distributed airflow
Low partially-conditioned air energy cost
Mechanically balanced – doesn’t unbalance the house
Known fresh air source
Cons
Best with fully ducted ventilation ducting (High cost)
The system must be balanced on installation and checked periodically
Requires filter maintenance
Requires active homeowner involvement.
MOISTURE CONTROL
Airtight homes without fresh air ventilation become humid with moisture from the occupants in a couple of days from moisture control:
• Cooking
• Showering
• Breathing
• Cleaning
• Dishwasher• +80% RH, Rots wood & blisters paint
• +75% RH, Cups wood floors & stains walls and ceilings
• 60+%RH: Mold and mildew can grow.
If the house is sealed tight with spray foam, it is much harder for this moisture to leave the house naturally. It builds up inside the home, raising relative humidity to uncomfortable and dangerous levels.
Optimum relative humidity range to minimize harmful contaminants*(a decrease in bar height indicates a decrease.
Whole House Moisture Control Strategies
Lower thermostat temperature in order to remove humidity control strategies.
• Variable Speed A/C
• Whole House Ventilating Dehumidifier
Lowering thermostat temperature in order to remove humidity
Why is overcooling a problem?
• Can create cold surfaces that lead to condensation, mold, or other damage.
• It is expensive, 10% higher per extra degree of cooling.
• Wear and tear on the air conditioning unit – adds unnecessary run time to the equipment.
Lowering the thermostat temperature to remove humidity makes matters worse, the air conditioner’s run time is reduced due to the spray foam’s effective thermal insulation, meaning less ability to remove moisture.
Variable Speed A/C
• Slows air conditioner blower down to remove more moisture.
• A/C makes a smaller amount of colder air.
• Colder surfaces (ducts, registers, etc.) may form condensation.
• Does not solve 70ºF/raining scenario.
Whole House Ventilating Dehumidifiers
• Remove excess humidity
• Provide precise time & volume control of fresh air.
• Match air filtering requirements to needs.
• Are quiet and draft-free.
• Provide make-up air for exhaust devices.
• Provide a slight positive pressure to the house.
Ventilation and Moisture Control in Spray Foam Insulation? Spray foam insulation has been
increasing in popularity over the last
several years due to :
• Becoming more affordable
• Significant long-term energy savings
Sealing restricts air movement through the building envelop.
