As Seen on Bay Area Living & Kron4 – Continuing the HVAC Discussion

A well-performing building envelope controls rain, air, heat, and vapor on the inside of a building. In addition, it must support the building to resist and transfer dynamic loads of the structure, and its finish should meet the aesthetics desired both inside and outside.

Rain and vapor control is the job largely performed by the roof and walls; heat flow control rests mainly with the ceiling, and air control includes the roof, walls, doors, windows, ceiling, and even the foundation of a building.

The effectiveness of a building envelope can be measured by its ability to protect against weather and climate, the level of indoor air quality it maintains, its durability, and its energy efficiency. To achieve these objectives, building envelopes ideally need to have a solid structure, an air barrier, a vapor barrier, a thermal barrier, and a drainage plane.

A heat pump can use a basic cycle for air conditioners and refrigerators in addition to water heaters, too – the flow of heat is just reversed when used for heating applications. While electrical resistance heaters used to be more popular than they are today, they have been gradually replaced with heat pumps, which offer significant improvements in energy efficiency.

Heat pumps require evaporators and condensers in order to perform. The pumps use a refrigerant to help absorb heat where it vaporizes – in the evaporator – then they release that heat where the refrigerant condenses – in the condenser. Insulated pipes allow the refrigerant to travel, producing efficient thermal energy transfer across various distances.

Oversized HVAC Systems

Bigger is not always better – especially with heating and cooling systems. Oversized cooling systems, for example, can create a clammy house because they don’t run long enough to dehumidify the air, they have shorter lifespans because they turn on and off so often, and they are more expensive to run and to install. It should be noted that the Energy Star New Homes program requires systems that are no more than 15% oversized for residences.

HVAC Load Calculations

The right way to size an A/C unit is with Manual J, a protocol developed by the ACCA (Air Conditioning Contractors of America). This method, which was once done by engineers with pen, paper, and slide rules, is now almost always done with computer programs. Other contractors using 500 square feet per ton are often installing an air conditioner that is 2, 3, or even 5 times larger than it should be. The techs at A-1 Guaranteed Heating & Air, Inc acknowledge that most newer homes, even in hot climates, have loads of 800 square feet per ton or more. Cooler climates and/or well designed high-performance homes can be as high as 1500, 2000 even 2500 square feet per ton.

At A-1 Guaranteed we use Right-Suite Universal by Wrightsoft. Contact us if you’d like more information about how we can help you with your HVAC project.

Displacement Systems

These systems supply air directly to occupied areas at low velocities for minimal mixing. Displacement systems are ideal for ventilation and cooling of large areas and high spaces where energy can be saved if only the occupied zone below is treated.

Displacement room airflow uses the difference in air density between an upper zone and lower zone to stabilize the temperature and humidity of the air. Convection creates vertical air motion into the upper zone to not only move heated air higher, but also to move contaminants up and away from occupants in the lower zone. Since supplied air is moved directly into occupied space, the air temperature of the supplied air must remain higher than that in mixing systems – usually above 63 degrees F.

You’ll want to focus on two tasks when it comes to attic insulation: increasing the amount and sealing air leaks in the ceiling. The payback for upgrading attic insulation and sealing air leaks can be as short as three years. Radiant-reflective insulation is popular for homes these days because it makes the attic dust-free for storage, keeps blown-in insulation from blocking rafter bays, and reduces the radiant heat gain from the roof.

Although blown-in loose-fill insulation is not as commonly used as batt insulation, it can be installed quickly and will completely cover the ceiling. Loose fill can also be blown in over any existing insulation. Interested in reading more on the topic? Click here to read our blog.

Static pressure is the pressure of airflow anytime air is moving in any direction within a duct system. It can also be thought of as the resistance to airflow in an HVAC system’s ductwork and components.

Tools that use this technology include infrared cameras (IR cameras), thermal imaging devices, and thermographic scanners. A professional who uses the device is a thermographer, and the image produced by IR cameras is called a thermogram.

Many people think that these devices measure surface temperatures of buildings; however, this is incorrect. What they measure is the intensity of infrared energy, otherwise known as radiant energy, that is being emitted by the surface at which it is aimed.

• An airtight home helps avoid moisture condensation issues.
• Air leaks in a non-airtight home reduce energy efficiency, increasing energy consumption.
• Airtight homes prevent uncomfortable drafts caused by air leaks.
• Establishing proper air tightness helps determine the amount of mechanical ventilation that will be needed to provide good indoor air quality.

A blower door is a fan that mounts into the frame of an exterior door. This powerful fan pulls air out of a home, which lowers the indoor air pressure. Higher-pressure outdoor air flows through any unsealed openings and cracks, which can be detected by an auditor using a smoke pencil or gauges.

There are two types of blower doors: calibrated and uncalibrated. Calibrated blowers should always be used by auditors because it has several gauges that measure the amount of air that the fan pulls out of the house. In contrast, an uncalibrated blower can only locate leaks, not measure them.