House as a System

Presented By: Andrew Woodruff

0 What is a house?

A house is a system of interdependent parts: • One part affects many others – Cause and Effect relationship • When they all work together, the house is – Safe – Durable – Comfortable – Efficient

1 The House as a System

THE HOUSE AS A SYSTEM Multiple Systems Pressure Boundary Thermal Boundary Heating & Cooling Ventilation Appliances Homeowners Mother Nature

Courtesy of Building Performance Engineering 2 Grandma’s House (Enclosure)

3 Examples Building Envelope (Enclosure)

An un-insulated attic ... Makes the heating and cooling system work harder than necessary

4 Examples Building Envelope (Enclosure)

Leaky recessed Increase heat loss/gain, lighting fixtures... and can cause ice dams

5 Examples Building Envelope (Enclosure)

This bathroom exhaust The moisture condenses does not exhaust to on the roof deck and outdoors – just to the soffit trusses causing damage

6 NOT System Thinking Building Envelope (Enclosure)

When we insulate & vent the attic without air sealing And rot the roof When we air seal without insulating And grow mold on the drywall When we air seal without attention to the forced air system And the pressures get out of control NOT System Thinking Building Envelope (Enclosure)

When we tighten up and get a new And end up with no fresh air When we do our air sealing and install a ventilation system …that the occupants don’t understand or think they need NOT System Thinking Building Envelope (Enclosure)

When we do air sealing without combustion safety testing And (sooner or later) hurt somebody When we install a clothes dryer in utility room And backdraft the water heater When we install more heat to solve a heat loss problem And waste time and money Credit: David Keefe SYSTEM Thinking Building Envelope (Enclosure)

A comfortable, safe, and energy-efficient home requires: A well-sealed air boundary. A fully insulated thermal envelope. The thermal and air boundaries to be continuous and in contact with one another. Efficient, properly sized equipment to condition the living space and heat water. A well-designed and balanced air distribution system. Healthy . An educated client. House as a System Building Envelope (Enclosure)

Building Envelope

Mechanicals

Occupants

11 Thermal & Air/Pressure Boundary

For maximum efficiency and comfort, the thermal and air barriers must be continuous and in contact with each other. The Building Envelope Building Envelope (Enclosure)

Envelope Separates conditioned space from unconditioned space

13 Building Thermal Envelope (Enclosure) BASICS Building Envelope (Enclosure)

Consists of an and a thermal barrier.

Be sure to address critical junction areas. Building Enclosure Heirarhcy House as a System

Enclosures are made of assemblies that are made of materials i.e., Assemblies • Floors • Walls • Ceilings Materials • Kneewall • Studs, Drywall, Insulation, etc.

• Credit: Allision Bailes, EV Blog

15 Visual Inspections Building Envelope (Enclosure) BAD Envelope! Visual Inspections Building Envelope (Enclosure) BAD Envelope! Visual Inspections Building Envelope (Enclosure) GOOD Envelope!

Vapor retarder faces Insulation touching air warm in winter side barrier = good envelope

Tiger claw bends down and secures the batt without compressing it. Visual Inspections Building Envelope (Enclosure) Recessed Light Fixtures

Photos courtesy of The PA WTC Visual Inspections Building Envelope (Enclosure) BAD Envelope! Visual Inspections Building Envelope (Enclosure) BETTER Envelope? Visual Inspections Building Envelope (Enclosure) NO….BAD Envelope! Visual Inspections Building Envelope (Enclosure) GOOD Envelope! Mechanicals Building Envelope (Enclosure)

24 Visual Inspection Leakage Testing Visual Inspection Duct Leakage Testing Visual Inspection Duct Leakage Testing Visual Inspection Duct Leakage Testing Ventilation Ducting Ventilation

Excessive length of duct installed causing sharp bends. Increases effective length and reduces airflow. 180° bend = min 30’ Mechanicals Building Envelope (Enclosure) When working properly these are the systems that make our homes more durable, healthy, and comfortable: Heat and cool the space Add or remove moisture Remove pollutants Provide ventilation Provide creature comforts such as hot water

30 Combustion Appliance Zone Testing Air Movement – Building Science Basics

This test is done to determine if there is a possibility of a Combustion Appliance back-drafting because of….. Worst Case Scenario: Duct Leakage ( On) Door Closures Exhaust Fans /Equipment 31 Combustion Safety Ventilation

Can Create combustion appliance problems! Occupants Building Envelope (Enclosure)

33 Baseload Energy Use Building Envelope (Enclosure)

The energy used by electric or gas appliances in a home that is not used for space conditioning, thus not a seasonal load.

Typical Measures include: Lighting Retrofits. Refrigerator Replacement. Water Heater Modification Low-flow Fixtures.

34 Building Science Basics Building Envelope (Enclosure) 2nd Law of Thermodynamics

Energy will ALWAYS move in a predictable manner ….from high to low

– Heat Flow: hot always moves to cold

– Moisture Flow: moisture always moves to dry

– Air Flow: Air always moves from an area of high pressure to an area of low pressure Heat Flow Building Envelope (Enclosure) Types of Heat Flow

• Conduction = Objects must touch

• = Air movement

• Radiation = Happens between surfaces with different temperatures that “see” each other Through a Wall Building Envelope (Enclosure) Uninsulated Conduction

Convection

Radiation

HOT COLD

Conduction

Insulated Heat Transfer Definitions Heat Movement – Building Science Basics

BTU = Measurement of Heat Energy needed to raise one pound of water one degree F Approximately the amount of energy produced by a typical kitchen match Delta T or ΔT = Difference in Temperature R-Value = Resistance to Heat Flow U-Factor = Amount of Heat Flow through one square foot of material with a one degree F temperature difference across the material U = 1 / R

39 Air Movement

40 Old vs. New

The old house got wet in the summer The new house gets just as wet but can’t dry; (humid) & dried in the winter (low ). therefore poor IAQ and mold/mildew.

Photos courtesy of The US Department of Energy 41 Something to Think About

New Houses: • Are more airtight. • Have more exhaust appliances. • Have “weaker” natural draft combustion appliances. • Have less drying potential.

Diagram courtesy of John Tooley 42 Air Flow Air Movement – Building Science Basics

Airflow is measured in cubic feet per minute. Also written as ft3/min, or CFM.

1 CFM OUT = 1 CFM IN.

Airflow takes the path of least resistance.

Air moves from high- to low-pressure areas.

43 Units of Measuring Air Flow Air Movement – Building Science Basics

Cubic Feet per Minute (CFM) Rate of air flow Based on the size of a home and the number of occupants, a home should have a certain amount of fresh air when the home is closed up

3-Dimensional 1’ x 1’ x 1’

A way to quantify air movement.

44 How Many “Boxes per Minute” Air Movement – Building Science Basics

45 Air Leakage Air Movement – Building Science Basics

Pressure Difference Air Leakage

Hole

46 Air Leakage Air Movement – Building Science Basics

Direct Leakage IndirectIndirect Leakage Leakage

47 Air Leakage Air Movement – Building Science Basics

Ventilation: Controlled air leakage

Exfiltration: Air leaking out (exit)

Infiltration: Air leaking in

48 Visual Inspections Building Envelope (Enclosure)

Ventilation = Controlled air leakage

Infiltration = Exfiltration = Air leaking in Air leaking out (exit) Driving Forces of Air Leakage Driving Forces of Air Leakage Driving Forces of Air Leakage

Driving Forces of Air Leakage

Temperature and pressure differences – usually between inside the house and outside

The bigger the temperature or pressure difference, the greater the air and heat flow

51 Air Leakage: Pressure Driving Forces of Air Leakage

P = Pressure Difference

Positive Negative

Flow is from ______positive (high) to ______negative (low) pressure For every CFM that ______,exits one CFM ______enters Flow takes the path of ______least resistance 52 Driving Forces Driving Forces of Air Leakage

WIND DIRECTION

Exhaust Fan

Wind Heat Fans

53 Driving Forces: Wind Effect Driving Forces of Air Leakage

WIND DIRECTION

positive negative pressure pressure

Wind creates a Which creates a positive pressure on negative pressure the windward side of on the other sides the building . . . of the house

54 Driving Forces: Driving Forces of Air Leakage

Stack Effect positive pressure

Neutral pressure plane

negative pressure

55 Positive pressure Stack Effect (with reference to outside) Neutral pressure plane

Negative pressure • David Keefe DavidVermont Keefe Energy Investment Corp. (with reference to outside) Vermont Energy Investment 56 Corp. Driving Forces: Fans Driving Forces of Air Leakage

Exhaust Fans

Exhaust Fan

negative pressure

57 Driving Forces: Ducts Driving Forces of Air Leakage

Duct Leakage

Return Supply

58 Driving Forces: Ducts Driving Forces of Air Leakage

Interior Door Closure

Return Supply

59 Moisture Movement

60 Moisture Flow Moisture Flow – Building Science Basics

The biggest factor in building durability A major influence on indoor air quality and health

61 IAQ and Relative Humidity Moisture Flow – Building Science Basics

Relative Humidity and Indoor Air Quality Relationships Decrease in bar width indicates decrease in effect

Bacteria

Viruses

Fungi

Dust Mites

Respiratory Infections

Allergic Rhinitis and Asthma

Clinical Interactions

Ozone Protection

Percent Relative Humidity 0% 10% 20% 30% 40% 50% 60% 70% 80% 90%

62 Moisture Sources Moisture Flow – Building Science Basics People, Pets, Plants Bath, Kitchen, Laundry Unvented combustion appliances Lack of moisture protection in building Rainwater protection & drainage, roofs, foundations, crawlspace vapor retarders and capillary breaks

63 Courtesy of Building Performance Engineering Types of Moisture Flow Moisture Flow – Building Science Basics

Capillary Bulk Transport Sucked through porous Solid or liquid, gravity materials Water Vapor Diffusion Carried by air Through a solid

64 Relative Humidity & Condensation Moisture Flow – Building Science Basics

Relative Humidity = The amount of water in the air relative to the amount the air could hold at its current temperature 100% RH = dew point = condensation Warm air can carry more water than cold

65 Relative Humidity Moisture Flow – Building Science Basics Understanding Relative Humidity vs. Change in Temperature 40°F 70°F 90°F

100% RH

45% RH 25% RH

66 Courtesy of Building Performance Engineering Dew Point/Condensation Moisture Flow – Building Science Basics

67 Diffusion vs. Air Leakage Building Envelope (Enclosure)

100 sq ft wall without

Vapor Diffusion: 1/3 pint per heating season

Air Leakage (1/2”hole): 30 pints per heating season

Courtesy of Building Performance Engineering Moisture Movement Building Envelope (Enclosure)

Air flow

Air molecules are blocked.

Both water vapor and air molecules Water vapor pass through. molecules are passed.

Diffusion Through Surface Convection Through Holes Crawl Space Case Study Moisture Flow – Building Science Basics

Symptoms Wet wood. Condensation on foundation surfaces. Possible Reasons High ground moisture source. Warm humid air entering vents from outside.

Crawl space surfaces are Water droplets of condensation on AC ducts. below the dew point of the Photo courtesy of PA WTC outside air.

70 Control Strategies Moisture Flow – Building Science Basics

Control strategies:

1. Keep indoor relative humidity reasonable

2. Keep indoor air from contacting cold surfaces

3. Ventilate

71 Summary Moisture Flow – Building Science Basics

The first step in doing a moisture assessment is to look for visible signs of moisture and moisture sources in the house.

Measure relative humidity.

Understanding the effects of temperature and vapor pressure on RH can help identify solutions.

Source control, air sealing, ventilation, and thermal improvements are important moisture mitigation strategies.

Photos and diagnostic equipment help document existing conditions.

72