Core Building Advances: Introduction to Sustainable Building & Building Science

Transcription

1 Core Building Advances: Introduction to Sustainable Building & Building Science Rob Howard & Mike Mongeon Habitat for Humanity International

2 Introductions Name Affiliate/Role Goals for the class

3 What is sustainability? Sustainable Building or Green means the process of providing homes with methods, products, and processes while preserving the natural environment to meet future needs. It means designing and building homes that will last, use less resources (energy, water, materials), are healthy to live in, and affordable in sustainable communities. Simple, Decent & Affordable means homes that are energy efficient, healthy, durable, and affordable.

4 Why build sustainably? To be good stewards of our natural resources and our planet (God s creation) Habitat Mission Principles: Promote transformational and sustainable community development. Create more affordable and healthier homes with our families. Take better care of our environment, our homeowners, and our volunteers. A home is not affordable if it is not energy efficient, healthy and durable throughout the life cycle of the home.

5 The truth about green

6 Building science scope Outside our scope Life safety (including disaster resistance) Structural integrity (engineering) Our scope: Comfort Affordable (low utility bills) Healthy (good indoor air quality) Durable Sustainable How: High performance homes control heat, air & moisture/water flow

7 Managing heat, air & moisture flow Guiding Principles High goes to low Hot goes to cold Wet goes to dry High pressure/temp goes to low 1 cfm out = 1 cfm in Boundaries control movement (ie. No Boundary = No Control) Movement needs 3 things: Source + Driving Force + Hole

8 Heat (thermal) flow HOT COLD Conduction is transfer of heat through a solid material or materials in physical contact Convection is the transfer of heat by the movement of air Radiation is the transfer of heat through space from a hot surface to a cold surface

9 Conduction Heat energy is bridged through un-insulated wood framing

10 Convection Heat energy transfer loop by mass motion of a fluid such as air or water

11 Radiation

12 Boundary: insulation/thermal envelope Thermal boundary = Insulation + windows Build air barrier in contact with thermal barrier Common problems Air sealing

13 Air flow High pressure or temperature Low pressure or temperature Conditions for Air Infiltration Pressure difference Exhaust fans Closed interior doors Duct leakage Temperature difference Outside to interior Unconditioned space to interior Boundary: Continuous air barrier

14 Boundary: air sealing Save energy and money typical air infiltration can account for up to 10% of a home s heat transfer in the hot humid climate Reduce air transported moisture damage Improve comfort Build tight, ventilate right Sources of Infiltration Before After

15 Major air leakage sites

16 Moisture flow Wet Dry Water as Liquid Bulk Capillarity Water as Vapor Diffusion Infiltration

17 Moisture flow - bulk Continuous Drainage Plane Capillary breaks stop movement of ground water into the building Foundation Drainage

18 Moisture flow - vapor

19 Boundaries for an efficient home Air Flow Heat Flow Moisture Flow (Vapor, Bulk) Air sealing Air barriers Tight ducts Pressure balancing Air sealing Air barriers Tight ducts Low-e windows Proper insulation Mitigate thermal bridging Radiant barriers Air sealing Air & vapor barriers Right-sizing Dehumidification Water management Ventilation

20 The house as a system Limiting and directing heat, air, and moisture flow Source + hole + driving force Reduce size of holes in boundaries Reduce driving forces Implications for Indoor air quality, durability, energy efficiency, and comfort Multiple benefits from individual improvements