Monthly Archives: July 2016

Follow Up Thought for Friday’s Summer Cooling Tips.

DeeDee and I started outside. The info from the back deck did not make the cut and I let it slide when i did the blog summary of her story.  So …

Shade Works

This is an Infrared image on one of my first new homes.  The 2 foot cantilever bay clearly shows the effect of the shade. There is a 20° F difference in the temperature between shaded and unshaded areas of the wall. The high temperatures on the side of the house are in the area of 128° F.  It is 97° F when I took this one.

Shade works.  Building a new home with a south facing set of large windows. It is worth your money to have a deck with a roof, or pergola over it. If you have an existing home, the Pergola is a great idea.

Concepts like this have been recommending in my Home Energy Audits.

Why The Way your AC is installed Matters! Part I

Screen Shot 2016-06-24 at 8.49.56 AMThe Air Conditioning Contractors of America (ACCA) publishes ANSI Standards for HVAC Contractors to follow. These professional standards are well known in the Home Performance Industry and the HVAC Contractors.  I found a link on their website this morning to a study showing the problems caused with problems that can easily occur if the Industry Professional Standards are not followed.

I covered a study from California about these types of faults recently. This one was completed by NIST.  The National Institute of Standards and Technology, a part of the US Department of Commerce.

CookA quick review of the reports shows many technical details and mathematical formulae.  That forms the back ground for comparisons with other studies.  However, they did write in some plain English for the rest of us. Here is one of their findings, about the performance of heat pumps.

A Heat Pump provides both heat and air conditioning. It is efficient because it moves heat.  In the summer, it moves heat from inside to outside, just like an ac unit.  The same technology and principals. In the winter they move heat from outside to inside. Yes, there is heat outside at cold temperatures.

Think about your refrigerator. When it gets up to around 40° F inside, the unit turns on and finds the heat in that 40° temperature and moves it out of the refrigerator to keep your food cool and fresh. If you watch your temperatures outside, you know more heating is done at 40° and above than at 20°.

This findings for a heat pump cooling your home apply to geothermal heat pumps, regular heat pumps and to air conditioners. They are all working on the same principals.

The first fault they report on is having the wrong size unit.

Changing the size of the heat pump for a given house – either undersizing or oversizing – impacts the heat pump performance in several ways:

  • Cycling losses increase as the unit gets larger; the unit runs for shorter periods and the degraded performance at startup has more impact (parameters used in simulations are: time constant = 45 seconds, or CD ~ 0.15).
  • In the cooling mode, the shorter run periods impact the moisture removal capability (i.e., ability to control indoor humidity levels) because operational steady-state conditions are an even smaller portion of the runtime fraction.
  • In the cooling mode, continuous fan operation with compressor cycling greatly increases moisture evaporation from the cooling coil. However, this impact is minimal with auto fan control (indoor fan time ‘on’ and ‘off’ the same as that of the compressor), since only a small amount of evaporation occurs with the assumed 4 % airflow during the off-cycle with the indoor fan off. If the air conditioner controls include an off-cycle fan delay – that keeps the fan on for 30-90 seconds after the compressor stops – then the impact of off-cycle evaporation is in between these two extremes (Shirey et al., 2006). The results in this study assumed auto fan operation with no fan delay.
  • Heat pump sizing also affects the level of duct losses.

A improperly sized unit will run for shorter periods, and will turn on and off more often. That is just like driving your car around downtown Wichita. Lots of stop lights. Compare you gas mileage to highway driving at a steady speed of 55 mph or higher.

OK, I know efficiency isn’t as important as being comfortable. So the next item is the comfort side.  Running you AC like your car in Down Town, doesn’t remove the humidity as well. Your house temperature is cool, but the humidity is high and you turn down the thermostat again to get rid of the humidity. Pretty soon you are cold, and yet you are not comfortable because you feel the high humidity.  Then you go out and buy a de-humidifier.

The third item is also a comfort issue. That is the advice of many HVAC technicians to set your AC fan to run continuously. When the AC shuts off and the fan keeps running, the humidity the AC just removed from your house is put back in. Oops!

DadBabyESFinally the report mentions duct losses. They are important in a home that has no basement. In those homes ducts can be located in the attic or the crawl space, or both. If you have one of those houses, I would be glad to address that one in the comments. So leave a comment if your are interested.

How do you get a right sized AC unit?   Your HVAC contractor can run a series of calculation found in the professional standard from ACCA Manual J.  It is a Load Calculation.  For cooling it considers the insulation in your home, the windows and size of the home and other details. It can be done on a paper worksheet or a spreadsheet. Both are free from ACCA. Most contractors have a software program to run these Load Calculations.

Load calculations for cooling, are a balancing act. The homeowner wants a home that is cool in the summer and in Wichita, they want the humidity controlled.  Without a lot of formulae or detail, how do, the rest of us, understand a cooling Load Calculation?

My advice is to look at the out door design conditions that must be factored into the calculation.  For cooling, ACCA Manual J has 6 outdoor conditions.

  • Two relate to location. Cooling in Atlanta, is different from Wichita and is different from Denver.
  • One is the outside temperature. The choice is a temperature that covers all but 1% of the hours in a year that require cooling for that location.
  • There are four design conditions that relate to Relative Humidity.

This obviously requires a balance. If your contractor varies from these conditions, it still must balance.  You may or may not like the balance, if one item is changed without consideration of the others.

What should you as a consumer do?

Insist that professional standards be used.

Require that all the items of the standard be measured and reported.

For Air Conditioning the standards require measurements of:

  • Air Flow Actual compared to manufacturer’s requirements. (+/- 15%)
  • Air Flow Static Pressure (ESP)  Actual within the manufacturer’s acceptable range
    • AND
  • No more than 25% or 0.10 IWC over the design pressure for the duct system.
  • Refrigerant Charge Verification
    • Superheat method:  Within +/- 5% of manufacturers superheat value.
    • Sub cooling method: Within =/- 3% of the manufacturers subcooling value.
  • Measured line voltage and low voltage circuits for voltage and amperage. These values shall be within the manufacturer’s requirements.

If you have good air flow in some rooms and not enough air flow in other rooms, your home has an air balancing problem. Have your system checked and balanced. This is known as test and balance or TAB. I have done test and balance work. Generally, the air flows should be within 20% of the design or application requirements.

Hey! It’s Hot Out There! — A conversation with@KWCHDeedee

Interview

 

 

DeeDee from Channel 12 KWCH called Friday morning looking for someone to talk about holding the line on cooling costs as the summer heats up.  We met Friday afternoon at a home in NW Wichita. This 4 year old home was larger than most in the Wichita area. 1800 SF on the main floor with a full basement. The Heating and Air is provided with a ‘Geothermal’ Heat Pump.  This system uses the 55 degree water under ground to provide heating, air conditioning and during these oppressive heat days in July, 2016 – de-humidification.

When I got there, the HVAC techs were there working on the system. It had shut off. The temperature in the home was 80° F and the relative humidity inside was in the lower 50% range. They reported the system was now running and during my time with DeeDee we felt and saw the system working. After a couple of hours, the temperature had dropped to 78°F and the relative humidity was down to 48%. The outside conditions at 2:30 pm, while I was there were a temperature of 98° F and a relative humidity of 45%.  Remember that humidity is relative, thus a higher temperature has the capacity to hold more moisture.  At 8:30 am Friday morning the outside temperature was 81° F and the relative humidity was 75%. Much higher than the inside RH at the same temperature when I arrived.

Not Comfortable

Not Comfortable

I think everyone was glad that the air conditioning had been restored.

DeeDee wanted some quick, easy to do, items for any one to help hold the electric bill down during the hot days of summer.  So we went around the home and we looked at some simple, low cost, easy to implement changes that could be made. These would work in you home as a home owner or in a rental home or apartment. We also looked at several improvements that should be considered.

Where does our energy get spent? Here is a graphic that was in my training text.
HHPie

The variations in percentages are due to differing house sizes, energy costs and types, and lifestyle choices.

Under the quick and easy category, people usually look at lights, electronics, and the thermostat.  Each of these requires the person in the home to do something. Turning out the lights, or turning the TV off, or setting the thermostat higher in the summer.  All of them save energy and thus lower your bill.

I classify all of these and others under the heading of Conservation. Then there are those that fall under the heading of Efficiency. These are things like adding insulation to your home, replacing your weatherstripping on doors/windows, or replacing a furnace / ac unit that is over 15 years old.

The difference: Conservation is changing how people work! Efficiency is changing how things work!  Both are important.

A quick summary of the summer conservation items would be:

  • Turn things, like lights and electronics, off when you aren’t using them.
  • Turn the temperature in the house up and turn a fan on.  Ceiling fans are great. If you need some ideas on ceiling fans, I wrote about them.
  • Reduce or eliminate excessive heat sources in the home. Turning off lights is great. Changing an incandescent to a CFL or LED saves energy and reduces the heat put into the home.
  • Another Heat Source is the Water Heater.  Turn it down to 120 degrees. Most people take a shower at 105° F. A 50 gallon tank with a medium flow shower head will provide 1 person with a shower of more than 30 minutes, with a typical mid efficiency recovery time.
  • Cooking inside produces heat and moisture.  Use a kitchen exhaust fan to remove both of those. They make your AC work longer.
  • Use the fan in your bath room to remove the heat and humidity when you shower.
    • if your fans noise level bothers you, replace them with a quiet fan. In Wichita the bath fans are selected and furnished by the electrician. The code requires 50 CFM to be removed from the bathroom.  Since electrician’s are trained in volts and amps, our common practice, means the person selecting your bath fan will bring the least expensive one. You might consider telling your builder on a new home, to have the HVAC contractor bring a quiet fan that will actually remove 50 CFM.
  • Move tasks that generate heat, such as baking a cake or washing and drying clothes to cooler parts of the day. In the morning or after nine at night are good times.
  • Use a clothes line to dry clothes, instead of the dryer.  In the summer do not dry them inside. That will just increase the humidity and make your AC work more.
  • At least one area electric utility has a demand charge for using electricity in the hot day times of the summer.  It is not Westar Energy. If you use another electric Utility, check your bill inserts, check their website, call customer service, and know when not to use electricity. A demand charge is an extra charge for usage during a specific time. Instead of 15 cents, you could be paying several dollars per unit.

Turning electronics off, such as your TV or computer, also involves the various accessories.  Computers have a printer, and sometimes other items that are plugged in. Along side your TV is a cable box, a DVD player, and other plugged in accessories. using a smart strip will help. A smart strip is a power strip that is controlled by the main device in the group.  So you plug your computer into the primary, and the printer, the monitor and other accessories into the other plug ins.  Now when you turn the computer off, the smart strip shuts the accessories off.  The same with the TV, or a game center.

The longer term changes you make to your home, cost more, and can have a larger impact.  These are the efficiency items.

  • Buy Energy Star certified appliances when you replace your refrigerator, washer and other appliances.
  • If your refrigerator or deep freeze is over 12 years old, I would strongly recommend that you look at replacing it.  The technology is changing fast and competition is holding prices down. Those made in the last 2 years use considerably less electricity then older models.

The largest portion of your energy use from the Pie Chart (above) is heating and cooling your home. The chart shows 45 – 55% of your energy use for this.

The simplest, and easiest to work on, would be the insulation in the attic. Others would include replacing less efficient equipment, considering the use of an exterior solar shade, or other improvement. After the work is done, you can sit back and enjoy your home.

Exterior Shade is a great thing, sometimes easy to do. Trees placed with shade considerations are great. Sometimes the builder can build some shading features into the home.  A wider eve for example. 30 inches instead of the standard 24.  Then the gutter, all work to extend the shade. The link below is to an Infrared image of shade from some builder included features.

Follow Up Thought for Friday’s Summer Cooling Tips.

We did take a look in the attic.  I found an attic that could use some attention. Some levels were in the 14 inch range, some were in the 10 inch range. One place had obvious density problems.  Insulation should be installed consistently level, certainly not lumpy. The fibrous insulation, fiberglass, cellulose, or rock wool, must be installed to the density specified by the manufacturer.  If not, you are not getting what your paid for.

attic

This is the attic from the KWCH video camera. I am reaching into a hole in the insulation and I can see the ceiling at the bottom of the hole.

I found no insulation card in the attic.  I can tell it is fiberglass and it is white. In the past two weeks, I’ve seen 5 different types of white fiberglass insulation.  If you install Johns-Manville Fiberglass, the three products I’ve seen in the past two weeks require 20 inches, another 16 inches and another 11.25 inches of thickness.  These depths would provide an R-49 level of insulation. This has been the requirement for attic insulation in our climate zone.  Since there is no legal requirement for insulation in South Central Kansas, most new homes are insulated to R-30 or less.

Call IR

This was the Infrared Image you saw in DeeDee’s video. I have reproduced it here with the visual light picture to help understand what it is showing.

I would like to thank DeeDee and Betty and Jack Call for their hospitality and seeing their home. I offered the Call’s a no charge Utility Usage Analysis for their hospitality. I will go back with that when I get the gas and electric usage from the utility companies.  Jack expressed some interest in adding some insulation to his attic so I will get some quotes for them to consider.

You can view the story DeeDee wrote and the video shown on the 6:00 news at the KWCH website.