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ARCH TECH
LECTURE 4 INFO
| Question | Answer |
|---|---|
| What is the primary form of thermal control in buildings? | Insulation |
| What does insulation do? | Prevents the movement of heat and in northern climates keeps heat inside during the winter and out during the summer. |
| What determines where condensation occur in a wall? | Heat flow and the location of the coldest surface. |
| Why does condensation form inside walls? | Moist indoor air hits cold surfaces and condenses. |
| What causes cold spots in wall assemblies? | Thermal bridges |
| Where do thermal bridges form? | Studs, slabs, and steel |
| What is thermal bridging? | Heat flow through conductive materials that bypass insulation. |
| Why is insulation between studs not enough? | It does not stop from thermal bridging. |
| What are the benefits of continuous exterior insulation? | Keeps sheathing warm, moves dew point outside wall, and keeps moisture in vapor form. |
| What happens to heat loss as insulation thickness increases? | Heat loss decreases |
| What happens to cost as insulation thickness increases? | Energy cost decreases, material cost increases and there is an optimal thickness. |
| What is thermal conductivity? | The rate of heat floor through a material. |
| What are the units of lambda? | W/mK |
| What does a low lambda value mean? | Better insulation |
| What does a high lambda value mean? | Poor insulation |
| Which type of materials have low lambda values? | Insulating materials like foam or wool. |
| Which conducts heat better copper or insulation foam? | Copper very high lambda at 380 |
| Which materials require less thickness for the same insulation? | Materials with low lambda values |
| Name factors beyond lambda when choosing insulation. | Cost, moisture resistance, fire safety, environmental impact, constructability. |
| What is the formula for R-value? | R = d/ lambda |
| What does the R-value measure? | Resistance to heat flow |
| What are the units of R-value? | m2K/W |
| What does a higher R value mean? | Better insulation |
| What is the formula for U value? | U = 1/R |
| What does U value measure? | Heat transfer through an assembly |
| What does a low U value mean? | Better thermal performance |
| How do you calculate total U value of a wall? | U = 1 / Rsi + E(d/A) + Rse) |
| What are Rsi and Rse? | Interior and exterior surface resistances |
| Why are Rsi and Rse important? | They account for heat transfer at surfaces |
| What is a homogenous wall? | A wall with uniform material layers |
| What is heterogeneous wall? | A wall with multiple materials (studs and insulation) |
| What tool is used for complex wall calculations? | PHPP Package House Planning Package |
Created by:
averylumgair