SPRAYFOAM Professional - Spring 2015 - (Page 49)

ABBA NEWS WHAT MAKES US COLD/ HOT/UNCOMFORTABLE? BY LAVERNE DALGLEISH, EXECUTIVE DIRECTOR, AIR BARRIERS ASSOCIATION OF AMERICA, INC. W e complain when we are too hot, too cold, too wet or too dry. Basically we feel uncomfortable and as we all want instant gratification, we go to the thermostat, adjust it and expect the HVAC system to respond immediately to our desire. Many times that is all we have to do, but in some cases it will not correct the situation and then we complain that the HVAC system in malfunctioning. What we forget in these cases, is that HVAC only deals with the air around us and the temperature and humidity of the air may be normal and at the correct settings. Many times we overlook basic building science and why we feel cold/hot and uncomfortable. We fail to remember that heat always moves from hot to cold and that for humans we radiate heat from our bodies and the rate of heat transfer is dependent on the temperature difference between our bodies and the surfaces around us. The air around us could be 70°F to 75°F, which should mean that we are comfortable. But the surfaces around us could be much colder. We know that heat doesn't rise - heat will always seek cold, which may not be in the up direction. Hot air does not rise by itself, it needs cold air to come in, sink to the bottom as it is heavier, allowing the hot air to rise by pushing it up. We can feel uncomfortable if we are standing on a cold floor, as an example, even though all of the air around us is 75°F. Our body is about 98.6°F and if the floor is 60°F, the heat flow is not from our body to the air around us but to the floor. We can even calculate the heat transfer rate between our bodies and the floor. We will feel cold as the heat is leaving our bodies at an accelerated rate compared to standing on a floor that is warmer. Hot air does not rise by itself, it needs cold air to come in, sink to the bottom as it is heavier, allowing the hot air to rise by pushing it up." If we remember that heat travels in three different ways - conduction, confection and radiation - and that the rate that heat travels is exponential as we go through the different ways, then we see why the temperature of surfaces around us become very important. When dealing with thermal insulation we generally think in terms of heat flowing by conduction. In fact, we talk about the resistance to heat flow in R-Values. We do this because the heat flow and therefore the resistance to heat flow is measured using ASTM C177 or ASTM C518. Heat flow by conduction is significantly faster as this method of heat convection moves heat from one surface to another surface through a medium. This sort of short circuits the normal heat flow by conduction. Heat flow by radiation is significantly faster than that as it moves heat from one surface to another surface without heating the space in between. So heat flow by radiation is significant 8' x 8' Test Wall 1/8"x6'-7" OSB joint at stud 8' OSB/CMU joint 8' OSB/top plate joint 8' OSB/bot plate joint 1-1/2" ID capped pipe Rectangular elec box 4" circular elec box 1/8"x8' horiz OSB joint 0 5 10 15 20 25 Air Leakage (L/s) at ∆P = 75 Pa www.sprayfoam.org | SPRAYFOAM PROFESSIONAL 49 http://www.sprayfoam.org

Table of Contents for the Digital Edition of SPRAYFOAM Professional - Spring 2015

Executive Director’s Corner
President’s Post
Foam Business News
SPFA Today
Industry by Design
Legislative Update
Why I Support SPF
Safety First
Energy Codes and the Benefits of SPF
Behind the Foam
SPF Industry Prepping for Code Changes in Sweden
How to Make Money and Have Fun Doing It
What You Need to Know Before You File in 2015
Tips on Spraying Foam – Are You Doing It Right?
Choosing the Right Strategy for Complex Construction Claims
10 Ways Your Company Can Use Instagram
ABBAA News
Ask the Expert
Calendar of Events
Index of Advertisers/ Advertisers.com

SPRAYFOAM Professional - Spring 2015

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