MEEB - heat flow

What is heat transferred between in conduction?

Heat is transferred directly from molecule to molecule, within or between materials, with proximity of molecules - material density - played a critical role in the extent of heat transfer.

What does F2 stand for in the heat lost formula?

Heat loss coefficient for the floor slab/installation configuration

What does F stand for in the heat loss formula?

Heat loss coefficient for the wall/floor/installation configuration a given depth below grade

What is of greater concern under dynamic conditions rather than static conditions?

Heat storage within a material.

What is the new thing that must be worried about with dynamic conditions?

Heat storage.

Which takes less energy to raise the temperature of? A low specific eat material or a high specific heat material?

It takes less energy to raise the heat of a low specific heat material

What happens when this air layer is disturbed?

It's resistance drops quickly. with a 15 mph wind resistance drops to about one quarter of the still air value.

Emittace is related to what?

Absorbtance

Where does the vapor barrier need to be installed?

As close to the warm side as possible. Typically just behind the interior surface.

What is heat gain?

The total instantaneous heat flow.

What does the SHGC depend upon?

The type of glass and number of pains, as well as tinting, reflective coating's, and shading by window or skylight frame.

The difference in what is the driving force behind waster flow through components of an intact building envelope assembly?

Vapor pressure.

Materials with low permanence are termed what?

Vapor retarder's. And are incorporated in envelope constructions as means of reducing the flow of water vapor and subsequently risk condensation of the vapor within the assembly.

What is shading coefficient based on?

Just the glass and not the frame.

Filling an en closed airspace with what has thermal benefits?

Krypton or argon

What is reflected back into the room by the selected film?

Longwave radiation reflecting off objects in the room.

Vapor pressure difference is take Layton heat flow as temperature difference is to what?

Sensible heat flow

What does U stand for in the design heat loss formula?

U factor for a given component

What is the one overall property that expresses the steady-state rate at which heat flows through architectural envelope assemblies?

U-value

How many air changes per hour does a type building house?

.25 air changes per hour

What is a CLO unit equivalent to?

.88 ft2 F/BTU or the Equivalent of a typical Americans business in 1941

What is the SHGC values for real products?

.9 to .2

What is the range of SHGC?

0 to 1 with one representing no resistance and zero representing total resistance.

What three types of heat flow are usually of primary interest?

A design heat loss based upon worst hour conditions which is used to size heating systems A design heat gain also based on worst our conditions which is used to set design cooling systems An annualized heat flow based upon your long climate conditions which is used to predict annual energy usage and costs and/or demonstrate compliance with energy standards.

What is the heat transfer process of conduction primarily depended upon?

A difference in surface temperatures

What is sol-air temperature?

A parent outdoor air temperature that would produce the same heat flow experienced under the combined effect of temperature difference - based upon actual outdoor air temperature - and radiation.

Where can you find a minimum outdoor air flow rates?

ASHRAE standard 61.1 and 61.2

One low E coating is almost as effective as what?

Adding another layer of glass.

What is convection highly dependent upon?

Air Motion so windspeed must be considered when estimating exterior surface convection.

What is the rate of outdoor air filters in between a new window and it's frame measured under defined conditions - usually under pressure equivalent to that of 25 mph wind with the window locked?

Air leakage

What must the aluminum foil face if it is to be as effective as a radiant barrier?

An air space

What does C stand for in this equation?

An approximate value of energy content under typical interior conditions.

What is calculation of design heat loss?

An estimation of the worst likely hourly heat flow from the building to the surrounding environment.

What does the LEED rating system require compliance with as a prerequisite to green building status?

Ansi/ashrE/iesna standard 90.1

Where is the energy code must likely to be encountered for nine residential buildings?

Ansi/ashrE/iesna standard 90.1

What are two answers to the challenge of switching?

Automated controls and making switches that are easy, fun, and obvious to use.

Would Houston be a good or bad candidate for an evaporatorative cooling strategy?

Bad

Closed shell with punched holes

Barrier dominated

What are some examples of flexible and semi rigid insulation?

Batt and blankets

Convection is heat exchanged between what and what?

Between a fluid - typically air - and a solid with motion of the fluid do to heating or cooling played a critical role in the extent of heat transfer.

It is possible to measure the actual infiltration performance of a constructed building using a device called a what?

Blower door. Some energy codes require the blower door test.

What is conductivity measured in?

Btu in./h ft2 F k W/m K W/m C

How is U factors calculated?

By finding the resistance of each part including air film and air spaces and then adding these resistance to obtain a total resistance. The U factor is the receptacle of the Sum of these resistances.

What is heat flow through basement walls and floors complicated by?

By increasing length of heat flow path with increasing depth. Also the temperature of the earth is not equal to the ambient air temperature and becomes more and more out of phase with air temperature at increasing depths.

How is conductivity established?

By laboratory tests and is published as a basic property of homogeneous solids

What are the two ways outdoor air can enter the building?

By means of infiltration and or ventilation.

At the exposed surface of solids heat transfer takes place by what two ways?

Convection and radiation.

What are the three principal ways to lose or gain heat?

Convection, conduction, radiation.

How do you calculate infiltration through cracks

Calculate the length of the crack on the Windward exposure and multiply this by the respective air assembly leakage rate

Insulated masonry systems

Can offer lower will you factors while preserving a masonry exterior - for weathering and appearances and a masonry interior for thermal mass.

What is the only distinct subset of seeking that must be handled at the time by a cooling system?

Cooling load

The insulation value provided by layers of air is often listed as what?

Conductance, the reciprocal of resistance.

Open frame with building skin selectively added

Connector dominated

What are infiltration and ventilation air flowrates expressed in?

Cubic feet per minute or liters per second

What are the most common and visible switches?

Day lighting/solar control devices

The higher the visible transmittance the greater the what?

Daylight transmission

The greater the LSG the more suitable for glazing is for what

Daylighting in hot climates.

What do you some of the most effective insulating materials combined?

Dead airspace and layers of reflective film. This is an inexpensive way to slow the flow of heat via radiation from hot space where the temperature differences are large.

What are the characteristics of a conductor?

Dense, durable, and able to diffuse heat readily.

What is the weight of a material per unit volume?

Density

Thermal capacity for material is obtained by taking the product of what two things?

Density and specific heat

What is heat storage and function of?

Density of a material and it's specific heat, the product of these two properties is known as thermal capacity.

What is the difference between designed for cooling load calculations and heating load calculations?

Design cooling load calculations must deal with many more variables including the compounding affects of solar radiation, which create the need for dynamic heat flow analysis. Things get very complicated.

What does change and P stand for in this equation?

Difference in vapor pressure between outdoor and indoor air

What is installed just inside the exterior surface material to block the flow of liquid water through the envelope? You can consist of simple tarpaper rebuilding felt.

Drainage plane

What kind of conditions are generally assumed for analysis of summer heat gain?

Dynamic conditions

Selective services sometimes used in someway collectors are highly absurd to it have a very low what?

Emittance

The more absorbent material the higher the what

Emittance

What are vapor will often need to be handled by a climate control system through the use of what?

Energy or latent heat

What refers to power usage overtime?

Energy.

Understanding what is fundamental to predicting thermal comfort?

Envelope surface temperatures.

What are some examples of formed in place insulation?

Expended pellets or liquid fiber mixtures that are poured Frost, sprayed, or blown in place.

What units should you use to estimate slab on grade floors heat flow instead of you factor?

F2 units - per foot or per meter of perimeter length

Went to objects are at two different temperatures heat flows from what to what?

From the hotter to the colder.

What are the 4 things norberg Shultz said can be thought of in terms of its design intent relative to the exchange of energies.

Filter Connector Barrier Switch and a new one: Transformer

Prescriptive path

For example a minimum R for wall insulation or maximum U for window.

What applications are high transmission low E good for?

For passive solar heating applications.

What is the fundamental principle of the vapor retarder?

For the retarder to stop the flow of water vapor before the vapor can you come in contact with its dewpoint temperature within the assembly.

If two spaces have two different moisture contents where does the moisture flow?

From the area of greater concentration to the area of lesser concentration.

What are two approaches to providing low e films

Hardcoat - durable, less expensive, but thermally effective and soft coat - better thermal performance but more expensive and subject to dig radiation by oxidation in the manufacturing stage

What happens when insulation gets wet?

He moves faster through if the air pockets are filled. Also moisture damage can occur.

What can be greatly reduced by the introduction of selective transmitter film somewhere within the glazing cavity?

Heat flow due to radiation

How does heat flow in radiation?

Heat flows via electromagnetic waves from hotter surfaces to detached colder ones - across empty space and potentially great distances.

the greater the design heat loss the larger the required what?

Heating system capacity

Three common types of low E coatings or what?

Hi transmission low E Selective transmission Low e Loe transmission low E

What type of SHGC is desirable for solar heating applications?

High

What does q stand for in the design sensible heat loss formula?

Hourly heat loss through a specific envelope component - by conduction, convection, and radiation - under design conditions

What is resistance measured in?

Hours needed for 1 BTU to flow through 1 ft.² of a given thickness of the material when the temperature difference is 1°F.

What are the two reasons design latent heat loss is often ignored?

Humidity is often allowed to float during the winter There is no single system or piece of equipment that can handle both sensible and latent heat loss.

Climate is condensation on cold interior surfaces occur especially windows?

In cold climates

When are radiant barrier's useful?

In east and west facing wall's in warmer climates Also in roofs in warm climates.

In what climate is the object to keep the moisture in the warmer outside air from penetrating the cooler and usually less humid interior air?

In humid climates.

When would you need to convert SHGC to SC?

In order to determine the overall shading performance of the glazing unit with external or internal sheeting devices.

What are the three broad categories of insulation?

Inorganic fibrous or cellular products such as glass, Rockwall, slag will, pure light, or vermiculite Organic fibrous or Silas products such as cotton, synthetic fibers, Kirk, filmed rubber, or polyester he Metallic or metallized organic reflective membranes which must face in airspace to be effective

What is cooling load equal to?

Instantaneous heat gain minus any part of that heat gain that is stored with in the building plus any previously stored gains that are now affecting air temperature.

What are some examples of loose fill insulation?

Insulating cement, a loose material mixed with the binder and traveled into place.

ICF

Insulating concrete forms Can be used to improve thermal performance. Rigid insulation that's protects both faces of the structural wall. Exterior and interior finishes her than applied to the insulation.

Where do you find the energy code for residential buildings?

International energy conservation code or model energy code

Air change method

Is it correlation method wearing observed performance of a set of existing buildings is matched to key characteristics of the proposed building. Very simple and quick but tends to over estimate.

What kind of heat does you factor address and not address?

It addresses sensible heat - heat flow resulting from temperature difference but does not address Latent - moisture related heat flow.

When air motion is minimal, what does an insulating layer of air do?

It attaches itself to the surface. The resistance of this layer of still air along a vertical surface is equivalent to that of a thickness of plywood.

How does evaporation carry heat?

It carries heat the way from wet surfaces, but this is much less influential for most buildings and for our bodies.

How does humphreys and Nicolas equation for indoor comfort differ from other comfort models?

It does not take relative humidity into account.

What is the relationship between SHGC and VT expressed as?

Late to solar gain ratio - LSG

What is sensible heat used to change the state of - evaporate or condense - water?

Latent heat

What type of SHGC is better for windows were cooling is the dominant thermal issue?

Lower

What should you be careful of when looking at precalculated values for doors?

Many doors are near forced air supply registers reducing the resistance of indoor air film. The exterior air film maybe more effective than I dissipated because the doors are typically protected by overhangs or porches.

What is the uniform temperature of the surrounding enclosure in which radiant transfer from the human body would equal the actual radiant heat transfer within the building space?

Mean radient temperature

Is thermal bridging more serious in metal studs or wood studs?

Metal studs.

Latent heat flow result in a change in what

Moisture content. Often humidity of the air.

What is the principal means of latent heat loss or gain?

Moisture flow through envelope assemblies and via air leakage.

Who is the standardized approach to reading windows coordinated by?

National fenestration rating council - NFRC

Is air leakage values required to be listed on NF RC labels?

No

Is there a recommended low humidity limit for the ASHRAE comfort zone?

No

Is the design heat loss the highest heat loss that can or will ever occur?

No. It is a statistical reasonable maximum heat loss based upon a chosen outside air temperature.

Shit did you factor be used for air to ground heat flow?

No. Just air to air heat flow.

How many air changes per hour does a leaky building have

One air change per hour

What are the two concepts that can illustrate a fundamental range of choices surrounding envelope intent?

Open frame and closed shell

Understanding temperature patterns with the materials is critical to establish being where what

Or water vapor might condensed within the wall roof or floors Assemble.

What does V stand for in the heat loss formula?

Outdoor air flow rate in CFM

What does P stand for in the heat loss formula?

Perimeter of the floor slab.

What does M stand for in this equation?

Permanence of envelope Element

The what of the material of construction is the latent equivalent of sensible conduction?

Permeance

What should not be on the interior surfaces when I drainage plan is used?

Plastic, final wallpaper or vapor retarder paints because the drainage plane must be able to wick to the interior.

What refers to the instantaneous flow of energy at any given time?

Power

What are the two paths to compliance energy codes can provide?

Prescriptive path and performance path.

The lower the heat admittance the lower the what?

Radiated heat exchange.

What is the cooling load?

Radiation heat flows that are absorbed and stored but internal mass of the building. Heat gain that affect air temperature at the hour of interest are this.

What four things can you reduce to design for energy efficiency?

Reduce component you factors - within the constraints of the budget and constructibility Reduce areas of components - within the constraints of the program and design intent Reduce the design temperature difference - usually by lowering indoor air temperature, perhaps by microclimate improvement. Reduced airflow into the building

What can thermal capacity do to heat flow the storage?

Reduce heat flow.

What is an important added benefit of low E glazing?

Reduction of UV transmission thus reducing fading of objects in room.

ASHRAE Comfort zones are primarily defined by what?

Relative humidity and dry bulb temperatures

In the winter it is not unusual to add water vapor to the air in the building to keep the what from dropping too low?

Relative humidity. This is accomplished by evaporating water by adding the latent heat of the vaporization.

Crack method

Requires more effort and more data. Also requires that all infiltration under design conditions is due to cracks around windows and doors.

How do you avoid thermal bridging and roof structure?

Roof insulation is placed entirely above or entirely below the supporting structure.

How do you convert SHGC to SC?

SC equals SHGC divided by .87

How does SHGC differ from SC?

SC is the ratio of radiant heat game through a given type of glass relative to 1/8 inch single clear glass. SC is still a useful concept for comparing glass types and especially for expressing

In the future structural systems may be changing due to the advent of what?

SIP

What is a form of energy that flows whenever there's a temperature difference and that manifest itself as an internal energy of atomic vibration within all materials?

Sensible heat.

Performance path

Set a minimum level of overall energy performance maybe met using a wide range of solutions.

What is testing of slab on grade floors related to?

Slab perimeter length.

What is the measure of the amount of heat required to raise the temperature of a given mass of material by 1°?

Specific heat

What are the three basic water systems?

Storage tank water heater Circulating storage water heater Instant/ tankless water heater

What are SIPs?

Structural insulated panels. Seeds in labor and increases thermal performance.

What is it called when all the concurrently available high-performance glazing options are combined into one product?

Super window.

What does A stand for in the design heat loss formula?

Surface area of the envelope component

Sensible heat flow results in a change in what?

Temperature

What are the two primary means of calculating the infiltration air flow rate during design?

The air change method and the crack method

The thermal gradient can be predicted by proportioning what?

The collective thermal resistance at any point in the assemble to the overall difference in temperature across assembly.

What is VT influenced by?

The color of the glass - clear glass has the highest VT ll as the coatings and the number of glazing's.

What does🔺t stand for in the design heat loss formula?

The design temperature difference between the outside air and the inside sir

What two things does sol air lump together?

The heat flow caused by radiation absorbed and retained by surface with the heat flow caused by air to air temperature difference.

What is the facility for rejecting he accumulated by your building?

The heat sink for the purposes of high mass cooling.

What does the concept of sol-air temperature help illustrate?

The impact of solar radiation on opaque construction assemblies

Who developed the building envelope commissioning guideline that is available via the whole building design guide?

The national Institute of building science

What variables will affect design cooling load? The palate?

The orientation of an assembly, The tilt of an assembly, The surface reflectance of an assembly, The thermal capacity of an assembly, The solar heat gain coefficient of a transparent/translucent assembly Shading for any envelope component He gained from occupants Heat gain from equipment

What is the (SHGC) solar heat gain coefficient based upon?

The performance of the entire glazing unit not just that of the glass portion.

What information is necessary to calculate the design of heat loss through buildings envelope?

The rate at which heat flows through each of the elements. The area of each of these assemblies The design temperature difference between inside and outside

EMittence

The ratio of the radiation admitted by material to that emitted by a black body of the same temperature.

What factors influence the U factor?

The size of the air gap between glazing's, the coatings on the glazing's, the gas filled between the glazing's, and the frame construction.

Greater density will permit what?

The storage of more heat.

Design for energy efficiency in the building envelope sensually consists of trying to reduce what?

The value of any variable that occurs on the right-hand side of these design heat loss equations.

Why are Krypton or argon good in the enclosed airspace in the glass?

There less conductive gases that greatly reduce heat transfer by convective currents producing lower u factor.

And analysis of heat flow under dynamic conditions involves what variable?

Thermal capacitance

What is an indicator of the ability of a fixed volume of material to store heat?

Thermal capacity.

What is the variation in temperature through a cross-section of the construction assembly called?

Thermal gradient.

What is the key determinant of steady-state heat flow?

Thermal resistance.

What is it called when users must base their actions in manipulating their thermal switches at some point in time and what the effect will be needed at a later time?

Thermal sailing

What are air films?

They are void of material, they have potentially useful thermal properties and contribute substantially to the insulating capabilities of some construction assemblies. All above ground and blue assemblies include at least two air Felms - interior and exterior

Why are the design conditions for building important to consider when initiating the design process?

They consider statistical extremes that may occur at the building site.

In the summer moisture will typically flow into an air-conditioned building increasing humidity and requiring the humidification which is accomplished through what

Through the removal of latent heat of condensation of the added mosture.

What is a measure of the delay inflow of a pulse of heat through immaterial the results from thermal capacity?

Time lag.

What is the job of the thermal envelope analysis?

To ensure that the proposed envelope will meet the design intent and criteria.

Where are low Emittance coatings usually applied?

To one glass surface facing into the air gap between multiple glazing's

What is the sum of sensible and latent heat flows?

Total heat flow.

What is The thermal/optical property represents the percentage of incident late - only the visible spectrum - at a normal angle of incidence that passes through a particular glazing.

Visible transmittance or VT

When the floor is exposed outdoor air like a cantilever or crawlspace that you factor is calculated the same as what

Walls and roofs

What kind of air rises and what kind of air Falls?

Warm air rises and cold air falls. Sue vertical surfaces will encourage surface air flow faster then horizontal services.

The less permeable a material is the greater the resistance to what?

Water vapor flow.

What applications are low transmission low e good for

Where the sun is the enemy.

What applications are selective transmission low E good for?

Where winter heating and summer cooling are both important.

Where else is he common to put the vapor barrier?

Within the insulation at a point about one third of the distance from the interior to the exterior. This allows the inner one third of the wall to be used as a Chase for wiring or plumbing without penetrating the retarder.

Where does the dewpoint usually occur?

Within the insulation layer

Can solar radiation and sound be comforted into heat?

Yes, within limits

Are selective transmission films available as separate sheets to go on storm windows?

Yes.

What is the calculation of latent heat loss through aboveground components?

q=(M)(A)(🔺p)(C)