how to find u-factors for both summer and winter in a hvac course

What is the “fudge factor” in cooling systems?

Jul 29, 2018 · When obtaining our U-Value, we must compare it with the value of the maximum (or limit) thermal transmittance specified for the climatic zone in which our project is located, in winter and summer.

What are U-factor and solar heat gain coefficient?

1) Summer: 73 to 79°F; The load calculations are usually based at 75ºF dry bulb temperatures & 50% relative humidity 2) Winter: 70 to 72°F dry bulb temperatures, 20 - 30 % relative humidity The standards were developed for mechanically conditioned buildings typically having overhead air distribution systems

What is the difference between SHGC and U factor?

Apr 28, 2011 · HVAC Right-Sizing Part 1: Calculating Loads Thursday, April 28 ... Find the hole that’s the closest match. 5. Size HVAC accordingly. HVAC Sizing Chart. ... common errors/safety factors – Altered outdoor/indoor design conditions – De-rated insulation, window performance,

What is a U-factor or U-value?

Mar 06, 2020 · HVAC System’s Age. If your system is more than 20 years old, then it’s probably not efficient anymore. Your heating and cooling system should last you from 15 to 20 years, depending on a few factors. An inefficient HVAC system can result in high energy bills and frequent HVAC repairs.

How do I calculate HVAC requirements?

6 Steps to Properly Size Your HVAC UnitStep 1: Calculate the square footage of the area to be cooled. ... Step 2: Next, multiply the square footage obtained for each area by 25.Step 3: Then, add 400 for each person who works in that particular area.Step 4: Finally, for each window, add 1,000.More items...•Jul 7, 2016

How do you find CLTD?

CLTD (corrected) = CLTD (table) + (78-Tr) + (Tm-85).

What is U-value in thermal insulation?

A U-value is a sum of the thermal resistances of the layers that make up an entire building element – for example, a roof, wall or floor. It also includes adjustments for any fixings or air gaps.Oct 5, 2016

How do you set up Astairs and downstairs thermostats in the summer?

During the summer, set your upstairs thermostat to your desired temperature, and the downstairs unit two degrees warmer. During winter, set the downstairs temperature to the ideal level, and upstairs two degrees colder. During the winter, this isn't as much of a problem, because you want a warmer home.Jun 4, 2018

What is CLTD factor?

The first of the cooling load factors used in this method is the CLTD, or the Cooling Load Temperature Difference. This factor is used to represent the temperature difference between indoor and outdoor air with the inclusion of the heating effects of solar radiation.

What is a cooling factor?

The amount of aerosols in the air has direct effect on the amount of solar radiation hitting the Earth's surface. Aerosols may have significant local or regional impact on temperature.

Is a higher or lower U-factor better?

The lower the U-Factor, the better the window insulates. The SHGC measures how much of the sun's heat comes through the window. It can range in value from 0 to 1. The lower the SHGC, the less solar heat the window lets in.

Is U-value better higher or lower?

The lower the U-value of an element of a building's fabric, the more slowly heat is able to transmit through it, and so the better it performs as an insulator. Very broadly, the better (i.e. lower) the U-value of a building's fabric, the less energy is required to maintain comfortable conditions inside the building.Dec 13, 2021

What is the difference between R-value and U-factor?

U-value (also known as U-factor) is a measure of heat transfer (heat gain or loss through glass), while R-value is a measure of heat resistance. U-value is not a material rating; it is a calculation of the conduction properties of various materials used in the construction of windows, doors and skylights.

Why is my upstairs so much hotter than downstairs in winter?

Cold air is denser than warm air so it stays on the bottom while warm air rises. That's why the downstairs can feel so chilly while the upstairs is toasty in the winter.Dec 11, 2020

Why is my upstairs so much hotter than downstairs?

Blame physics: hot air rises while cold air sinks. That means your upstairs typically gets hotter than your lower levels, even if your air conditioner's working in overdrive. Your roof's hot, too: Unless you have shady tree cover, your roof absorbs a ton of heat from the sun.

What temperature should you set upstairs and downstairs thermostats?

The general rule of thumb for a two-story home is that you should set each thermostat two degrees Fahrenheit apart from the other. During the summer, when your AC is running, set the upper floor at the temperature you actually want in your home. Then set each floor underneath that to two degrees warmer.Aug 12, 2020

What is the U factor?

Less frequently, the U-Factor may also be referred to as the U-Value. Now we are getting somewhere. The U-Value or U-Factor measures how much heat a window, including the frame, glass, and insulating materials, allows out of the house, which is also known as its thermal transmittance.

What is the U factor in windows?

What is U-Factor? U-Factor and Solar Heat Gain Coefficient (SHGC) are the two most important factors in choosing energy efficient windows. The U-Factor determines how well your windows keep warm air inside. The Solar Heat Gain Coefficient is a measure of how much outside heat is blocked from coming into your home.

Why are gases heavier than air?

Gases are heavier than air and therefore provide insulation resistance to air. That means the gases effectively block the air exchange between outside and inside. Manufacturing and an attention to detail in the construction of a window makes a great deal of difference in the U-Factor as well.

How to get a warmer home?

To get a warmer home go with a lower U-Factor, such as 0.30 or 0.15 even. For parts of the home that are extremely warm even in winter, go with a lower low Solar Heat Gain Coefficient. The windows vary in the combination of U-Factor and Solar Heat Gain Coefficient to accommodate just such variations in the home.

Why is the U factor important?

The U-Factor is important regardless of the climate. Though, it is most important for homes in places where there is a great deal of reliance on heating the home. This includes mostly the Northern climate. It is also important in places where it gets cold, such as the North Central and South Central.

How much of the floor space should be skylight?

For these reasons, the rule of thumb is minimize the skylight size to only five percent of the floor space. If there is little other natural light from windows, then 15 percent is a good ratio.

What is the difference between R and C?

This usually refers to the insulation in an attic or the walls. C-value is the thermal conductance - how long it takes for the whole temperature of a material to change when the surface is heated.

How to design an HVAC system?

But for all projects, to some extent, the following major steps have to be taken:#N#1. Determine all applicable design conditions , such as inside and outside temperature and humidity conditions for winter and summer conditions, including prevailing winds and speeds.#N#2. Determine all particular and peculiar interior space conditions that will be maintained.#N# 3. Estimate, for every space, heating or cooling loads from adjacent unheated or uncooled spaces.# N#4. Carefully check architectural drawings for all building materials used for walls, roofs, floors, ceilings, doors, etc., and determine the necessary thermal coefficients for each.#N# 5. Establish values for air infiltration and exfiltration quantities, for use in determining heat losses and heat gains.# N#6. Determine ventilation quantities and corresponding loads for heat losses and heat gains. #N#7. Determine heat or cooling loads due to internal machinery, equipment, lights, motors, etc.#N#8. Include allowance for effects of solar load.#N#9. Total the heat losses requiring heating of spaces and heat gains requiring cooling of spaces, to determine equipment capacities.#N#10. Determine system type and control method to be applied.

Why are HVAC engineers not necessary?

This is usually not necessary, because of the great number of variables involved in the design process. Strict design criteria will increase the cost of the necessary machinery for such optimum conditions and may be unnecessary. It is generally recognized that it is impossible to provide a specific indoor condition that will satisfy every occupant at all times. Hence, HVAC engineers tend to be practical in their designs and accept the fact that the occupants will adapt to minor variations from ideal conditions. Engineers also know that human comfort depends on the type and quantity of clothing worn by the occupants, the types of activities performed, environmental conditions, duration of occupancy, ventilation air, and closeness of and number of people within the conditioned space and recognize that these conditions are usually unpredictable.

What is conductance used for?

Conductance is usually used for assemblies of different materials, such as cast-in-place concrete and concrete block with an airspace between. The flow of heat through such an assembly is very complex and is determined under ideal test conditions.

Which law states that heat flows from a hot to a cold object?

Heat always flows from a hot to a cold object, in strict compliance with the second law of thermodynamics (Art. 13.2). This direction of heat flow occurs by conduction, convection, or radiation and in any combination of these forms.

What is thermal conduction?

Thermal conduction is the rate of heat flow across a unit area (usually 1 ft2) from one surface to the opposite surface for a unit temperature difference between the two surfaces and under steady-state conditions. Thus, the heat-flow rate through a plate with unit thickness may be calculated from

What is the term for the amount of cooling that has to be accomplished to keep buildings comfortable in hot summer?

These conditions are, respectively, termed the “indoor design condition” and the “outdoor design condition”.

What is load calculation for cooling and heating?

In principle, the loads are calculated to maintain the indoor design conditions. The first step in any load calculation is to establish the design criteria for the project that involves consideration of the building concept, construction materials, occupancy patterns, density, office equipment, lighting levels, comfort ranges, ventilations and space specific needs. Architects and other design engineers converse at early stages of the project to produce design basis & preliminary architectural drawings. The design basis typically includes information on:

What is the best way to keep out the sun?

Venetian blinds, roller blinds and other operable shades are a low-cost and effective solution for keeping out the sun. A light colored blind reflects some of the solar radiation and absorbs the rest. If the blind is in the room, most of the energy it absorbs is added to the room's cooling load.

How is solar heat gain calculated?

Solar heat gain through glazing is a sum of the transmitted radiation and the portion of the absorbed radiation that flows inward. The solar heat gain is estimated by a two-step process. 1) For conduction and 2) the heat gain due to solar radiation transmitted through or absorbed by glass.

Which climates have the highest potential to use external spaces?

In tropical and arid climates there is a high potential to make use of all external spaces, whereas moving towards the northern latitudes the external spaces have to be covered to be used.

Where should the atrium be located in a building?

In the tropical zone the atrium should be located in a way to provide ventilation within the built form. In the arid zone the atrium should be located at the center of the building for cooling and shading purposes. For the cool and temperate zones the atrium should be at the center of the building for heat and light.

How does tinting glass work?

The properties of a given glass can be altered by tinting or by applying various coatings or films to the glass. Glass tints are generally the result of colorants added to the glass during production. The tints absorb a portion of the sunlight and solar heat before it can pass all the way through the window to the room. Tinting is the oldest of all the modern window technologies and, under favorable conditions, can reduce solar heat gain during the cooling season by 25% to 55%. Both glass and plastic laminate may be tinted. "Heat absorbing" tinted glass maximizes its absorption across some, or all, of the solar spectrum. Unfortunately, the absorbed energy often transfers by radiation and convection to the inside.

How long does a HVAC system last?

If your system is more than 20 years old, then it’s probably not efficient anymore. Your heating and cooling system should last you from 15 to 20 years, depending on a few factors. An inefficient HVAC system can result in high energy bills and frequent HVAC repairs.

What happens if your HVAC system is too large?

Size plays an essential role in HVAC performance. If your system is too large for your home, the system will spend excessive time in its power-wasting startup phase, which results in short cycling. If the system is too small for the load of the home, the heater or air conditioner will spend excessive time attempting to reach the thermostat’s threshold, which it never does. Either way, poor sizing wastes energy. Our HVAC professionals can diagnose whether or not your system fits the load requirement of your home.

Consider Replacing Your HVAC System

You should consider the age of your heating system and your current energy bills before you do anything. Heating systems that are more than 10 years old are only 40-60 % efficient. If your HVAC system is on its last legs, seriously consider replacing the entire HVAC system.

Clean or Replace Air Filters

Dirty HVAC filters restrict airflow and reduce the entire efficiency of the HVAC system. If you have not cleaned or changed the air filters of your system for a while, now is the perfect time to do it. This should be done every 1-3 months.

Clean and Unblock All Vents and Registers

Go around your home and make sure all of your return and supply vents and registers are clean and clear. Double check that none of them are blocked by rugs, furniture, or closed off in any way. Learn why you should never close any of your vents and other common HVAC misconceptions.

Reprogram the Thermostat

When you start transitioning from cooling to heating, it’s a good idea to reprogram your thermostat. You can save a lot of money with a smart or programmable thermostat — you just have to make sure it’s set properly.

Home Heating Fire Prevention

Heating equipment causes around 56,000 home fires every year. Make sure your family is safe from home heating accidents by following these heating safety tips:

Professional HVAC Inspection

Have you serviced your heating, ventilating and air-conditioning (HVAC) system for the winter period? Whether you are a homeowner or a property manager, you will need to find a reliable HVAC professional to help you service your HVAC system.

HVAC Maintenance Agreement

An HVAC maintenance agreement, such as our Maintenance Value Plan (MVP), is a great way to keep your system at peak performance. Having an HVAC maintenance agreement not only gives you the advantage of priority service in the event of system failure, but also ensures that your checkups are done on schedule.

When is the best time to make sure your air conditioner is ready for winter?

Use these tips and techniques to ensure your air conditioner operates effectively and efficiently all summer. When the warm season draws to a close, it’s time to make sure your heating system is ready for winter.

Why is my HVAC system loud?

HVAC systems aren’t usually silent while operating, but they shouldn’t be loud, either. A cracked or partially broken belt is a common source of noise. A faulty ignition can make a whining sound. These are signs that it’s time to call out an HVAC technician to perform some home A/C troubleshooting.

How much more polluted is indoor air than outdoor air?

Did you know that indoor air is two to three times more polluted than outdoor air? It’s pretty alarming, especially when you consider that 90 percent of the average American’s life is spent inside.

Why does my air conditioner turn on and off so quickly?

Is your air conditioner suddenly turning on and off quickly? It could have a problem known as “rapid cycling condition.” This may be an indication that there’s an issue with the wiring, thermostat or ignition.

How hot does a 90 degree heat feel?

Humidity plays a big role in how hot you feel: 90° F heat can feel like 132° F at 100 percent humidity [4]. The key to maximizing your A/C system’s dehumidification capacity is keeping the drainage line clear.

Is it better to have the sun shining through your window?

Sun shining through your window may be beautiful, but that bright scenery comes at a price: higher cooling costs. The light carries heat into your indoor spaces. Keep it outside with energy saving blinds.

Can an air conditioner break in the summer?

A broken air conditioner in the middle of summer can be inconvenient and uncomfortable. But it’s often times a preventable problem. Here are some signs to watch out for that it may be time for an HVAC tune up.

How to control interior temperature?

The excess energy needed to pull down the interior temperature to the set point can be controlled to a certain extent by: 1 Parking in the shade. 2 Expert window tinting for all windows. 3 Shade screen insert for top window, and also adding top insulation. 4 Using windshield solar shade.

Who is Danny from Solar Energy?

Danny is principal research scientist at the Florida Solar Energy Center where he has worked for the last thirty years. His research for the U.S. Department of Energy has concentrated on advanced residential efficiency technologies and establishing the feasibility of Zero Energy homes (ZEH) — reducing the energy use in homes to the point where solar electric power can meet most annual needs. The opinions expressed in this article are his own and do not necessarily reflect those of the Florida Solar Energy Center, the University of Central Florida or the U.S. Department of Energy.

Is Royal Mail 100% electric?

Royal Mail has announced the launch of its first 100% electric Delivery Office. The Bristol East Central Delivery Office recently had its 23 diesel delivery and collection vans replaced by fully electric ones. The office's

Is Tesla Model 3 air conditioner variable speed?

Keep in mind that the air conditioner in the Tesla Model 3 is a fully variable speed compressor. I’ll repeat that so you can really hear it: the cooling system in the car is fully variable speed. This means anything you can do to make it run more slowly will save power — although, not in a linear fashion (like other variable speed compressors).

Significance of Design Criteria

• Achievement of the desired performance of any HVAC system, whether designed for human comfort or industrial production or industrial process requirements, is significantly related to the development of appropriate and accurate design criteria. Some of the more common items that are generally considered are as follows: 1. Outside design temperatures: Winter and summer Dr…

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Design Criteria Accuracy

Outline of Design Procedure

Temperatures Determined by Heat Balances

Methods of Heat Transfer

Thermal Conduction and Conductivity