Your roof acts the same way.  It can easily reach 150º or hotter on a sunny day.  This heat will then be re-radiated through the attic and will be absorbed by your attic insulation causing high energy bills and comfort issues.

This video illustrates how a radiant barrier works – plain and simple.  Rather than absorbing the radiant heat from the roof, let’s bounce it back and keep the attic insulation cooler. If you keep the insulation cooler, then less heat enters the home and you save money and stay more comfortable.

Think of it this way:  Radiant barrier is your 1st line of defense against radiant heat and your attic insulation is your 2nd line of defense against conductive heat.  They will actually work TOGETHER for maximum efficiency and comfort.

Click here to view the embedded video.

Looking for more videos on this topic? Check out my posts below.

External unit of a ductless mini-split

Sometimes you can do all this plus more and STILL have comfort issues.  It may never get comfortable or it’s freezing one minute and then too hot a few minutes later.

If you have given up and are ready to throw in the towel, then take another approach. You may  benefit from a Ductless Mini-Split Air Conditioner.  What’s a Mini-Split?  The best description is a  window air conditioner WITHOUT the window. If you have ever traveled to the Caribbean or the Orient you see them EVERWHERE.  The most common brands are Mitsubishi Mr. Slim, Sanyo, Daikin, LG, and Fujitsu just to name a few.

Ductwork is a very western idea. By using a ductless mini-split, you can easily bring more air conditioning (heat removal) to either an interior space or an exterior room without a noisy window unit.

Diagram of how a mini-split ductless system works

An air conditioner basically has three parts: 1) Compressor 2) Fan 3) Coil. A window air conditioning unit has all three together.  In a ductless air conditioner, the compressor is OUTSIDE and the fan and coil are INSIDE usually connected by a ¼” or 3/8” copper tubing.  The beauty it that the inside unit can be as far as 100 feet from the outside condenser.

Installation is pretty simple since there is usually NO electrical requirements for the inside fan coil.  Power to the inside unit is brought from the outside unit along with the refrigerant lines.  This means that basically you can drill a hole in a wall, run a 3” bundle of copper tubing, hang the indoor air handler on the wall, connect condensation tubing, set the outdoor unit, connect power and just like magic supply additional cooling and heating to any problem area.

Inverter vs. Non-Inverter Units

WARNING:  Mini-split air conditioners all look very similar but operate very differently. Traditional air conditioner units act like light switches – they are EITHER ON OR OFF.  They turn on, run for a while and turn off.  A mini-split with inverter technology acts like a DIMMER switch that automatically adjusts based on the required “load”.

Indoor portion of a ductless mini-split system

Inverter air conditioner units have several advantages.  First of all being comfort.  You will not have a big “swing” between feeling too cool and too hot.  Second is dehumidification.  By running longer at a lower level the inverter will pull more moisture out of the air resulting in better air quality and a “crisp” feel to the air.  Another advantage is energy efficiency.  Inverter air conditioners operate at a lower amperage and do not cause spikes in demand charge or light flicker when starting up.  Finally, the best feature of installing a mini-split air conditioner is CONTROL.  Whether it’s a bedroom, office or media room, you will be able to keep it cool and comfortable without having to cool the entire house.

Mini-split air conditioners are the fastest growing segment in the air conditioning industry.  Ease of install, efficiency, improved comfort and better dehumidification are just a few reasons never to throw in the towel on keeping comfortable.

Window with solar screen installed

One of the most frustrating problems is having comfort issues with a particular room in your home.  These are rooms that you can NEVER get quite cool enough no matter how hard you try.  The usual suspects are: Rooms over garages, bonus rooms, media rooms, master bedrooms that “stick out” from the house, and home offices.  In this article, I offer tips to help fix these problem rooms.

In order to fix the problem, you must first ask, “What exactly IS the problem”?

The easiest way to view any room is simply to look at it as a big box.  Heat enters the box and the air conditioner pulls the heat out.  The problem occurs when you combine several rooms (boxes) on ONE air conditioning system.  The airflow to each room will dictate how fast each room cools off.  The problem is that the sun, exposure, windows and internal heat loads (lights, people, computers, etc.) are DIFFERENT for each room and can CHANGE throughout the day. The “problem” rooms usually gain heat faster than the other rooms on the same air conditioning system.

Properly installed radiant barrier foil

There are two methods to TRY to fix this:  1) Keep the heat from entering in the first place or 2) Pull MORE heat out.

1) Keep the heat out – We want to STOP heat from entering so we don’t have to deal with it in the first place.  Start with the windows. If a window catches direct sun you need to shade the window.  Solar screens, window film, awnings or natural shade (trees) will all help – take your pick.  Then focus on the thermal envelope.  Walls should be well insulated and have some form of sheathing (usually ¾” foam board) on the ATTIC side of any walls to fully encapsulate the studs and the batts of insulation between them.  We call walls that face an attic “hot walls” for a reason.

Radiant barrier foil should be applied above and around any problem rooms. Ceilings should be sealed airtight and have plenty of insulation and ductwork should be checked for leaks or constrictions.

Open chaseway showing missing "blocking"

Finally, if the room is on the second floor, look for what is called an “open chaseway.”  This is the area between floors that usually has electrical, plumbing or ducts running through them.  Older homes often are missing “blocking” and allow hot or cold attic air to slide BETWEEN the floors and cook or chill the room from the bottom.  Open chaseways needs to be sealed up.

2) Pull MORE heat out – If you have done everything to keep the heat out and you still can’t stay comfortable, then the only other option is to pull more heat out. This usually requires the expertise of a good air conditioning contractor. You could need larger ducts, more ducts, additional return vents or a combination of these.

Unfortunately, on many “problem” rooms these measures have limited success. In fact, you can do EVERYTHING and STILL have comfort issues in some rooms.  What do you do?

Look for part 2 of this article: When all else fails – how to keep ANY room comfortable.

Return Duct with no seal

Everyday people ask me what is the single biggest thing they can do to improve efficiency and comfort in their home.

I usually ask a few basic questions like where they live, type of home etc.  Then I ask the two most important questions.  How old is the home and where are the ducts located?

When I hear “home over 25 years old” and “ductwork in the attic” big red flags go up.  Why?  Experience. I’ve helped thousands of people with home comfort issues and without fail this is the biggie.  Think of your house as one big refrigerator.  Leaky ducts are like leaving the door open.

Duct leakage is generally measured as a percentage.  For example, if you have 20% duct leakage this means that approximately 20% of the HOT or COLD air you are buying is being pushed OUT of the ducts and into the attic.  Or, duct leakage can also mean you are SUCKING hot or cold attic air INTO the duct system on the return side of the air handler. On new High-Performance homes, professional energy auditors are usually shooting for less than 2-5% duct leakage.  On older homes (especially with metal ducts) it is common to see duct leakage OVER 40%.

Older Metal Ducts with no seal

Why do older homes have such bad leaky ducts?  Back in the era between about 1950-1980 NOBODY cared about energy efficiency.  Energy was CHEAP, so installers usually didn’t bother to take the extra time or money to seal the ducts. For metal ducts this meant sliding two sections of duct together and using three screws to connect them.  Then, they would wrap the ducts with insulation to keep them from sweating or condensing moisture, not primarily to insulate them.

The ducts did not just start leaking; they were never sealed to begin with. If you have ever done some plumbing, this would be like connecting copper pipe together and NOT using solder on the joints.

As an example, think of an air conditioning duct as a long garden hose with a hundred holes in it.  Since water (or air in the ducts) is under pressure, the water will leak out of all hundred holes BEFORE it gets to the end.  Whatever does not leak out of the holes along the way is what ends up coming out of the end where you want it.  Air conditioning ducts are exactly the same and it’s pretty common to end up with only 50-75% of the air where we need it.

Older ducts – especially metal ducts are notorious for leaking.  Studies show that there is generally a direct correlation between the age of the duct system and the percentage of duct leakage.  Additionally, wrapping a duct with insulation does virtually NOTHING to reduce duct leakage just like wrapping a leaky pipe with a rag won’t stop a water leak.

AC Duct Leaks

Not only do leaky ducts cause higher energy bills, they cause most homes to go under negative pressure.  This means that if there is 20% leakage, then an equal amount of air must be “made-up”.  Make up air usually enters the home through windows, doors, can lights and any other “holes” in the home. Air quality can suffer since outside air is often dusty, dirty, pollen laden or humid.  Dust on windowsills or stains on carpet around the baseboards indicate outside air is being pulled into the home.

Some air-conditioning companies would rather sell a new air conditioner for thousands of dollars, rather than sealing/replacing ductwork for a fraction of the cost often neglects leaky ducts.

How To Fix Leaky Ducts

There are generally 3 methods to fix leaky ductwork:  1) Strip off insulation, seal all seams and then wrap with radiant barrier covered duct blanket.  2) Tear out metal ductwork and replace with flex duct.  This is usually not recommended since metal ducts are great (and expensive) if sealed correctly. 3) Strip off the duct insulation and have a spray foam company spray about 1-2 inches of closed cell foam on the ducts.  The foam will both seal and insulate the ducts in one shot.  WARNING: Check your local building codes and fire officials on this one.  Some cities do not allow this method.

Just remember to think of your home as one big refrigerator that you want to keep nice and cool inside.  Yes, you can add more insulation, or wrap it with radiant barrier, but bang-for-the buck, start by closing the door.

In an attic application, you should ALWAYS use a perforated product. Period.

Perforated Radiant Barrier Foil

Why? Solid products like bubble foil insulation are called “Vapor Barriers”.  A vapor barrier basically stops moisture from moving from point A to point B.  Or, another way to view this is that a vapor barrier will “TRAP” moisture.  I’m not going to get into the technical definition of what defines a vapor barrier (perm rating, etc), but here is an illustration of what IS and IS NOT a vapor barrier.

If you take a wet block of wood and put it inside a bag or an envelope made of perforated radiant barrier attic foil the wood block would eventually dry out.  Therefore, perforated radiant barrier is NOT a vapor barrier.  Moisture ALWAYS goes from wet to dry.  If you did the same test with the wood block inside a plastic bag the wood would still be wet months from now.  If moisture in its vapor form cannot pass through or object won’t “dry” then the product IS a vapor barrier.

Why is this important?

Virtually all (over 70%) of home issues are due to mold, mildew, rot, decay, etc. And moisture is the common theme here.  DRY products don’t grow mold, rot or decay. The bottom line is that moisture in wall and ceiling assemblies is not a good thing.  You want DRY walls and ceilings.

In cooler weather, the moisture INSIDE the home is greater than OUTSIDE.  Think cold and dry.  This is why our lips get chapped in the Winter and not in the Summer.  Since moisture will naturally move from wet (inside) to dry (outside) it will pass through sheetrock, insulation and then into a typical attic.  The LAST thing we want to do is TRAP moisture here.  Moisture, attic insulation and wood do not go well together.  A perforated radiant barrier will allow moisture to pass on through into the attic.  We want our attics to be cool and DRY.

Using a perforated radiant barrier will not change the effectiveness of the reflectivity.  Attic Foil has tiny pinholes about every ½ inch that allow for water in its vapor form to pass through (see picture).  These holes make up a TINY percentage of the surface area and will not change the effectiveness of the radiant barrier.

Solid products like bubble foil insulation are usually not perforated and are a recipe for disaster when installed inside an attic.  Solid (non-perforated) bubble foil is a great product when used correctly in applications like metal buildings.  The problem is that solid bubble foil products are often MISUSED in residential attics. This is especially true if the bubble type reflective foil products are laid directly over the attic insulation.  Moisture will pass through the sheetrock and will get trapped in the insulation below the bubble foil insulation.  This moisture will accumulate until it either condensates (turns to water) or freezes (turns to ice).

This is why it is critical to use a perforated tarp-like radiant barrier product. It will give you all the benefits of reflective insulation without the potential for moisture to get trapped.

I've written several other posts on this that you might be interested in. Check these posts below:

I put together a video to help illustrate how traditional attic insulation and radiant barrier WORK TOGETHER to make a home more comfortable and energy efficient.

Remember, traditional attic insulation – fiberglass or cellulose help to reduce Conductive Heat Loss.  A radiant barrier will help to reduce Radiant Heat Loss.  In cold weather, heat is lost in BOTH ways.

Combining good attic insulation and radiant barrier will give your home the best defense to stay warm in the Winter and cool in the Summer.

Click here to view the embedded video.

I've written several other posts on this that you might be interested in. Check these posts below:

The short answer is NO damage will occur. Tests have shown that installing a radiant barrier in attics generally only cause the roof and shingles to increase about 2° – 5° Fahrenheit.

This may seem unbelievable since radiant barriers are sold on the fact that they will reflect 97% of radiant energy away from their surface. The question is asked “Where Does The Heat Go?” It is assumed that since the heat is reflected back towards the roof then the roof must experience a significant increase in temperature.

Let me explain exactly what is happening between the sun, the roof (shingles & decking material), and the attic.

First, radiant energy from the sun heats up the shingles. The actual temperature of the shingles is primarily determined by two things: 1) Shingle color – darker shingles absorb more heat and get hotter, and 2) outside air temperature. Obviously, your roof will get hotter on a hot-sunny day compared to a cold-sunny day.

Once the heat is absorbed by the shingles, it is transferred via conductive heat flow to the roof deck. The roof then becomes a “sponge” to hold the heat. On the other hand, air has a cooling effect. How much is determined by the actual outside air temperature and the amount of airflow on the roof either by wind above the roof or attic ventilation below the roof.

These factors: Amount or Angle of the Sun, Shingle Color, Outside Air Temperature, and Airflow will determine the “Maximum Roof Temperature”. At this point, the roof will not get any hotter. Your geographic location will also affect this. A roof in Las Vegas will get hotter than a roof in Kansas. In general, maximum roof temperatures will range from 130° up to 180°.

I mentioned that the roof becomes a heat “sponge”. As the temperature goes up it will want to release the heat by converting it to radiant energy. This radiant energy is emitted in all directions, both upward to the sky and downward into the attic.

By installing a radiant barrier, the energy heading towards the home will be reflected back up towards the roof and cause MORE heat to be sent towards the sky away from the home. This is similar to a light bulb with a reflector behind it. The amount of heat and light given off by the bulb is constant, but you would feel less heat behind the reflector and the light is directed to one side.

Shingle manufacturers also provide a full warranty on products installed over radiant barriers. Your geographic location and color of shingles are the two biggest factors in determining roof temperatures.
The bottom line is that shingles usually see a SMALL increase in temperature (usually 2°-5°) over radiant barriers. These results are from tests performed by the Department Of Energy. Plus, many tests performed by customers and installers support this fact. This slight increase in roof temperature is considered nominal and will have virtually no impact on the performance or life expectancy of your roof. Rest assured, Your shingles will NOT BAKE.

I’m about to reveal the FOUR SILVER BULLETS for making your home more energy efficient in HOT CLIMATES. I’m especially talking about your typical one-story, ranch style home in the South.

Picture yourself sitting in your living room on hot August afternoon. The sun is beating down and it’s about 95º outside. What’s between you and the bazillion degree sun?
Four layers: 1) Roof 2) Attic 3) Leaking Ductwork in the Attic 4) Insulation
If you fix each “layer” between you and the heat from the sun, your home WILL BE MORE EFFICIENT AND COMFORTABLE EVERY TIME!!! Guaranteed. It is not complicated; just follow the recipe for success.

Radiant Barrier Installation

Layer #1 – Roof
Problem: It gets to be about 150º or more and basically acts like a big sponge to absorb heat. This heat is then radiated to the next layer.

Silver Bullet #1 = Radiant Barrier
Installing a radiant barrier is the next best thing to a giant tree instantly landing over your home. Your roof will still absorb the heat, but now rather than that heat being transferred to the home, it will be reflected AWAY.

Layer #2 – Attic

Blocked soffit vent blocks attic ventilation

Problem: Because most attics don’t have enough (or proper) ventilation, the AIR inside the attic basically gets “Clogged” like a drain in a bathtub. The air has nowhere to go and it just heats up and “fills up” the attic. Hot air in the attic will heat up the insulation AND heat up your ductwork that is supposed to have nice cold air running through it.

Silver Bullet #2 = Attic Ventilation
Attic ventilation is real simple. All you need is holes in the top and holes in the bottom. The more holes, the more outside (relatively cool) air moves through the attic and the cooler the attic air. The lowest the air inside the attic can go is near ambient (outside) temperature. The overlooked key to fixing attic ventilation is usually more soffit vents.

Leaking ducts in the attic

Layer #3 – Leaking Ductwork In The Attic
Problem: Putting Ductwork in the attic is about a dumb as making ice cream in the oven. Since you can’t move the ductwork, at least keep it from leaking. Most homes have duct leakage ranging from 15-50%. Older homes and homes with old metal ductwork usually have the highest leakage. What this means is that probably 25% or more of the cold air you are buying is being blown into the attic OR Hot dirty attic air is being SUCKED into your home if the leaks are on the return side of the AC system.

Silver Bullet #3 = Seal Ducts In Attic
If 30% of your water from your sprinkler were spraying into the street, you would fix it today. Why not do the same for your ductwork? Have your ductwork sealed or replaced. A tight duct system will save energy and increase comfort. Plus, indoor air quality will improve by reducing humidity and dust from being pulled into the home.

Attic Insulation being blown in

Layer #4 – Attic Insulation
Problem: Most homes do not have enough attic insulation to create a good thermal barrier between either the heat in the summer and the cold in the winter.

Silver Bullet #4 = Attic Insulation
Increase your attic insulation to the recommend level for your area. Check the DOE (Department Of Energy) for recommendations.

There you go. Four silver bullets for fixing your summer electric bill. Your attic is waiting.

I've written several other posts on this that you might be interested in. Check these posts below:

The answer: ZERO

Heat moves in 3 different methods:  1) Conductive 2) Radiant 3) Convective.  R-Value is a term used to measure how resistant a product is to CONDUCTIVE HEAT ONLY.  The best way to illustrate this is to picture an ice chest with a big block of ice inside.  Common sense tells us that WHAT the ice chest is made of and how THICK the walls of the ice chest are will determine how long it will take for the ice to completely melt.  An ice chest made of foam will obviously keep the ice from melting longer than an ice chest made of metal.  This is R-Value.

R-Value examples:  Wood has an R-Value of about 1 per inch of wood. So, three inches of wood has an approximate R-Value of 3.  Styrofoam has an R-Value of about 3-4 per inch resulting in an R-Value of about 11 for 3 inches.  This is why we don’t make coffee cups out of wood.  The coffee would not stay hot very long.

Radiant Barrier has NO R-value.  Why? Because R-Value is a measurement to determine the effectiveness of a material to slow CONDUCTIVE heat flow. It is an apples to oranges comparison. This is like asking how effective is an umbrella to protect you against the wind?  Obviously, an umbrella is designed to stop rain and not wind.  Just like a radiant barrier is designed to stop radiant heat as compared to conductive heat.

So, if radiant barrier has no R-Value, how is it effective?

Think of radiant barrier as SHADE.  Does shade have R-Value? No, but it sure is nice to have on a sunny day to help keep cool and comfortable.

Here is an example:  Let’s take two identical ice chests and fill them with ice.  Then, put one ice chest in the sun and the other in the shade. Which one is most effective in keeping the ice from melting?  The one in the shade, right?  Although the AIR TEMPERATURE will be exactly the same in the shade and the sun, the OUTSIDE SURFACE TEMPERATURES of the ice chest will be higher in the sun.  This will cause the ice chest in the sun to be less effective than the one in the shade.

If you were to wrap an ice chest with radiant barrier foil and put it in the sun, the foil would act like shade by reflecting 97% of the radiant heat from hitting the ice chest.  Decreasing the outside surface temperature is as effective as adding more insulation or more R-Value in most circumstances. Therefore, although radiant barrier by itself has NO R-value, it WILL increase the effectiveness of the existing insulation or R-Value.

Your home is very similar.  Regular insulation is like the ice chest and a radiant barrier will act like shade to keep the box cooler.  Install a radiant barrier to make the insulation in your home even more effective. Combining the two will maximize comfort and efficiency by slowing BOTH conductive and radiant heat flow.

I've written several other posts on this that you might be interested in. Check these posts below:

People always ask. “Should I Add More Attic Insulation or Install A Radiant Barrier”?  I hear this often and the answer is usually BOTH.

Regular attic insulation slows conductive heat.  Radiant barrier reflects radiant heat.  Your home gets a lot of both. Think of your home as a big refrigerator.  How much heat that flows in or out of this big box is determined by basically three things:  1) Inside surface temperature, 2) outside surface temperature and 3) R-Value and thickness of what is between the inner and outer surface.

The walls and top of the refrigerator (or your home) are typically insulated with “regular” insulation. Regular fiberglass or cellulose insulation slows conductive heat. Radiant Barrier acts like shade to reflect radiant heat and make the regular insulation more effective.  A perfect home would be built like a well-insulated refrigerator and be wrapped with radiant barrier foil insulation.  Common sense says that a refrigerator in the shade will use less energy than one in the direct sun.  This is because exterior surface temperatures can easily exceed 150º in direct sun.

If you decrease the outside surface temperature and reduce the difference between the inside/outside temperature, this has a similar effect on reducing heat flow as adding MORE “regular” attic insulation.

Too much of a good thing.

Getting attic insulation up to the recommend level for your area is always a good idea.  However, at some point you reach the law of diminishing returns.  Why?  Regular insulation slows heat, but it also HOLDS heat.  At the end of a hot-sunny day, the insulation in your attic can become a big, thick 130º blanket over the top of your home.  When the sun goes down, this “hot blanket” effect continues to hold and drive heat into the home. Once the roof cools down, the insulation can easily be the hottest part of your whole house. This can make your air conditioner run later into the night.  If you have marginal attic insulation, installing a radiant barrier will make what insulation you already have even more effective.

By combining good attic insulation and radiant barrier, you will get the best of both properties.  Reduction of conductive heat flow AND reduction of radiant heat flow by decreasing surface temperatures of the attic insulation.  Lower surface temperature is like putting the house in the shade.

So, for most homes I recommend doing both.  For maximum benefit, top off your existing insulation AND add a radiant barrier.  They will work together for maximum comfort and energy savings.

I've written several other posts on this that you might be interested in. Check these posts below: