December 27th, 2016



We encourage clients and real estate agents to call us with technical questions. We get lots of them – and the flavor of the month is condensation.

We don’t want to bore you with technical terms like vapor pressure differential. Let’s keep this simple.

There are two rules at work here:

1. When warm moist air touches something cool, condensation will form.
2. Warm air can hold a lot of moisture; cold air cannot. (While warm air can hold a lot of moisture, it doesn’t necessarily have to. Take a trip to Arizona).

Despite the threats of global warming, it’s still pretty cold outside in the winter. Consequently, windows are cold. If the inner glass surface is extremely cold, condensation (in the form of water or ice) will form, even in a house, which has normal indoor humidity. This, believe it or not, is the principle reason for storm windows. The exterior pane of glass provides enough of a buffer zone, that the surface temperature of the interior pane of glass stays warm enough, and condensation is less likely to form.

After doing what we can to raise the temperature of cool surfaces, we should turn our attention to reducing the moisture in the air. The easiest way to maintain low humidity levels is to buy an old house that is not particularly well sealed. Admittedly, the house might be drafty but the drafts mean that cold outside air is sneaking into the house. When that cold air warms up it will have very low humidity. Similarly, warm air that has picked up moisture from cooking, bathing, etc is flushed out of the house.

Unfortunately, this approach flies in the face of current thinking. Modern homes are sealed tightly because every bit of cold air, which leaks into a house means that warm air must leak out. This is not efficient.

Another way to get cold dry air into your house is to use up the warm moist air within. In many houses, air from within the house is used by the furnace, hot water tank and fireplace to create combustion and maintain proper draft up the chimney. This warm moist air escapes up the chimney causing cold dry air to enter the house and make up the difference.

Energy efficient homes don’t want to waste this inside air (which you have already paid to heat) by letting it go up the chimney. Consequently, most modern furnaces and fireplaces, bring in outside air for combustion, which increases efficiency.

Taken to the extreme, the most efficient house imaginable would not allow any cold outside air to leak inside nor would it use any inside air for combustion. While the heating bills would be low, the windows would be dripping with condensation and the indoor air quality would be terrible.


The high tech solution is to put in a heat recovery ventilator (also known as an air-to-air heat exchanger). As you exhaust the stale contaminated air from inside the house you replenish it with fresh air from the exterior. While the fresh air and the contaminated air are not allowed to touch one another, the heat from the exhaust air is transferred to the fresh air coming into the house.

In conclusion, condensation within houses requires two major ingredients – humid air and cold surfaces. If you increase the temperature of cold surfaces by adding storm windows and reduce the humidity levels by venting clothes dryers to the exterior, using bathroom and kitchen fans etc., you should be fine. If you still get a little condensation, go to the low tech solution. Open a window!

Contents of this site Copyright 2015/2016 Carson, Dunlop & Associates Ltd.

All rights reserved.

A Fall Furnace Primer – Part 2 of 2 – Humidifiers

October 1st, 2016


The outside winter air is cold and dry. The inside winter air is dry. Our chapped lips, dry skin and static zaps from doorknobs remind us of that all season long. Homes like the dry environment, but dry air makes people uncomfortable. While an ideal humidity for homes can be as low as 5%, people prefer about 60% humidity. And because people are more powerful than homes, we add humidifiers to have it our way.

Physics 101
If we asked Einstein what he thought about humidity, he might have said, “It’s all relative”. Of course, he said that about everything. We typically talk about relative humidity rather than absolute humidity. Relative humidity is the amount of water vapor in the air relative to how much vapor the air can hold before it condenses or rains. For example, a room with 4 pints of water vapor may have a relative humidity of 40%. This means we could have 10 pints of water in the air before the relative humidity reaches 100% and we get rain or condensation.

The interesting part is that if you cool down the air in a room but add no more water vapor, the relative humidity goes up. And, if you warm the air, the relative humidity goes down. This is important because the winter air outside is very cold and dry. When we bring the winter air into our homes and warm it up, we get really dry air in our homes. For example, outdoor air with 80% relative humidity at freezing temperatures will only have 20% relative humidity when we warm it to room temperature.


Do I need a humidifier?

If your house is new, you may not have a humidifier. You may not need one because the foundation and wood framing are still drying out, releasing moisture into the air. Also, new houses are “tight”, which means the air within them hangs around for a while before being replaced by dry exterior air. It hangs around long enough to pick up moisture from things like showers, cooking, drying clothes and breathing. By comparison, old houses are drafty. Cold, dry air is creeping in all the time, drying out the home as it flushes the warm moist air out.

Do I have one?

If there is a small box like the one in the picture hanging from the furnace or ductwork beside the furnace with a small electrical wire and a small water hose attached, then YES. You may also see the humidistat, a dial that looks like the thermostat but is used to control the humidity level, and is often mounted to the basement ductwork.

A drum type humidifier has a tray of water with a sponge barrel or drum rotating through it. The tray is kept full with a float switch, which allows water from the house plumbing to enter the tray when the water level drops. When the humidistat is turned up or the humidity level drops, a small electric motor rotates the sponge drum through the tray, absorbing water. Some of the air moving through the ductwork blows across the sponge, picking up moisture. This moist air moves through the ducts and into the rooms.

Cascade type humidifiers


Cascade type humidifiers have no tray of water. A small electric valve at the top controls the water supply to the humidifier. When the humidistat calls for water, the valve opens, trickling water down a honeycomb-like metal pad. Air blows across the pad, picking up moisture. Excess water is drained through a hose to a floor drain, laundry tub, or condensate pump.

What do I do?

If you have a drum style unit, the tray of sitting water is your nemesis. Ponding water will cause scale build-up and bacterial growth. Every spring, the water supply pipe valve should be turned off, the tray and sponge should be cleaned, and the humidistat should be set to OFF. In the fall, turn on the water valve, and set the humidistat to 35%. We recommend a mid-winter cleaning as well.
If you have a cascade style unit, turn off the water supply and turn the humidistat to OFF in the spring. Before use in the fall, remove and soak the pad in de-scaling solution. If it is damaged or too clogged to clean, the pad can be replaced. Once the pad is back in place, the water supply pipe valve can be turned back on, and the humidistat set to 35%. This unit will not need cleaning again until next year.

How much is too much?

As we said, people like about 60% relative humidity. Unfortunately, houses have a hard time coping with this in cold weather. Too little humidity makes people feel uncomfortable. Too much can cause condensation, mould, mildew, and rot as the warm moist air hits cool surfaces. What confuses many people is that as the weather gets colder, we have to LOWER the humidistat setting, even though we want to raise it. This is because the colder it is outside, the easier it is for condensation to form on cool surfaces like windows. We can reduce condensation by lowering the interior humidity level.

Humiditi level

Keeping an eye on the amount of condensation on your windows is another great way to gauge your house humidity level. You can also track things with a room temperature and humidity monitor, available at hardware and building supply stores.


Copyright 2015/2016 Carson, Dunlop & Associates Ltd.

A Fall Furnace Primer – Part 1 of 2 – Filters

September 1st, 2016

A Fall Furnace Primer

Beautiful September weather does little to remind us that winter’s cold breath will soon be upon us. While you’re in the basement unpacking the Halloween costumes, take a moment to consider your furnace.

Check the Switches
While it is probably okay, it’s not a bad idea to stroll over to your breaker panel and make sure the breaker marked “Furnace” is on. If your A/C was on recently, you can rest assured the breaker is okay. Then head back to the furnace and look for the switch that controls the electricity to the unit.

Most furnaces have a switch that looks like a light switch controlling the electrical supply. In a new house, the switch is often on a wall or a support about 6 feet above the floor, near the furnace. In an older house, the switch is often on the basement ceiling, or high on a wall, near the bottom of the basement stairs. This allows you to shut off the furnace quickly in the event of an emergency, without having to get near the furnace.

Now that you finally know what that mystery switch is, check to see if it is ON. If not, the heat will not come on no matter how high you set the thermostat. It is embarrassing to write a $75 check for a technician to come to your house and flip a switch.

It’s now time to focus on the two primary maintenance jobs for furnace owners: the air filter and the humidifier. We’ll talk about the air filter now and save the humidifier for the next issue.

Electronic filter


The Air filter
When the outside air makes its way inside, pollutants like dust, dander and spores are added to the air which has already been exposed to urban car exhaust, smog, dirt and pollen. The result is a thick, soupy haze…that is entirely normal. While most people aren’t bothered by the usual level of air-borne particulates, some are more sensitive, and everyone is affected if the level becomes excessive. To remove many of the larger particles from the air, your furnace is equipped with a filter.
Most filters are simply screens of paper, metal or plastic mesh that allow air through but trap most of the dirt. Some of these are thicker for more surface area, and some have specially treated media. Electronic air filters use electricity to electrostatically attract even smaller particles. They have a metal cover, an on/off switch, and may have an operation light. There are those that dispute the quality of the air cleaning abilities of standard household filters. These people usually sell high-end systems. For most houses the normal filters will do, and if nothing else they help keep the furnace itself free of massive dust accumulations.

Air filter

Where is it?
The furnace filter is typically a one to two-inch wide slot (for conventional filters) or a six to eight-inch wide slot (for electronic filters) in the ductwork immediately beside the furnace air return duct. If you don’t see such a slot, your furnace’s air filter is accessed only by removing the furnace and/or fan compartment cover. Turn OFF the switch to the furnace before removing any covers.
What do I do?
Once you have located the filter, pull it out to have a look. Turn off the switch on the electronic air filter before opening the cover. For a regular filter, if the mesh looks dirty and/or the unit is more than 3 to 6 months old, throw it out (paper media or fiber glass) or clean it (metal or plastic media). For an electronic filter, make sure you turn off the unit’s power switch. There will be two washable metal screens called pre-filters, then two electronic cells looking like layers of metal plates. These can all be soaked and washed, every one to three months. Careful of the fine wires running down one side of each cell…they are easy to lose or break. Regular cleaning of the air filter is important for your furnace and your lungs.


Copyright 2015/2016 Carson, Dunlop & Associates Ltd.

Home Repair Guide

August 1st, 2016

Undertaking a Home Repair

Let’s start by differentiating between a home improvement and a home repair. A home improvement, as the name implies, means improving something. It is usually a renovation to create more space, change the layout of the house, improve energy efficiency, or to make aesthetic changes. This report will deal with the simpler topic of home repair–basically replacing things that are worn out or fixing things that are broken. Here are some very basic rules to follow.


1. Know what you want done

If you are replacing a worn out furnace, for example, do some research to find out whether you want a mid-efficiency furnace or a high-efficiency furnace. If you are repairing a roof with a leaking valley flashing, determine whether you want the valley flashing replaced or just patched to last a few years until the whole roof needs re-flashing.

If you know what you want done, you can compare apples to apples when reviewing quotations. Otherwise it would be very hard to compare various quotes if every contractor has a different repair strategy.

Be prepared to stick to your guns. Many contractors will tell you that the job is much bigger, much harder, or it must be done his way (because if you don’t, it will be dangerous, or much more expensive the next time).

As home inspectors, we are often faced with contractor opinions that differ drastically from the recommendations in our reports. In most of these cases, the contractor is proposing unnecessary work.


2. Find at least 3 experienced, reputable contractors who are capable of doing the work

This may sound easier than it is. While it is best to rely on personal referrals from people you trust, these referrals must be taken with a grain of salt. Former customers of contractors are not usually in a position to comment on the quality of the installation of a furnace, for example. Also be sure the type of work that you are planning to have done is similar (in size and scope) to the work done for the person providing the referral. Many contractors who are geared to do major renovations are not well suited to do minor repairs and vice versa.


3. Obtain 3 written estimates

Our experience has shown that contractors quotes can vary as much as 300% on any given job. This is sometimes due to different perceptions of what needs to be done. This can be avoided by following Step 1 carefully. However, sometimes the variance is simply the result of how busy the contractor is.


4. Get three references from each contractor

Better than three references is a list of the recent clients that the contractor has worked for. That way you get to choose who you would like to select as a reference. Follow up with these references bearing in mind the comments in Step 2.

While you are at it, ensure that the contractor has appropriate licenses and insurance.


5. Choose the contractor

Don’t necessarily base your choice on price alone. Look carefully at what has been included in the estimates. Select the contractor with the best reputation, provided that the price for the job is fair. Avoid paying cash. The benefit of a cash deal is typically far greater for the contractor than it is for the homeowner.


6. Have both parties sign a contract

The contract should include a complete description of the work. It should also include details as to who is responsible for obtaining permits (if there is any doubt regarding the necessity of a permit, contact your local building department).

The contract should have a start date and a completion date. (On larger contracts, sometimes a penalty clause is included for each day the job extends beyond the completion date.)

The contract must also contain a payment schedule. The schedule should not demand very much money up front and the payment should be based on stages of completion as opposed to pre-determined dates.

Remember to hold back 10% of each payment for 45 days after the completion of the job to determine whether any liens have been placed on the property (as a result of the contractor not paying his sub-contractors).

Also, don’t expect much in the way of a guarantee if you are simply asking a contractor to undertake band-aid repairs. Many contractors will not simply patch a damaged valley flashing, for example, even if they are 95% sure that the repair will work. This is because there is still a 5% chance that they will get complaints to fix a subsequent leak. In fairness, the leakage is not their fault. They just do not want the hassles. Consequently, many contractors will suggest repairs which are overkill (replacing the entire side of the roof, for example) to reduce the potential for complaints. A significantly lower price can be obtained, if you explain to the contractor that you expect him to do his best, but you aren’t going to make him responsible for the future of the entire roof based on a $300 repair.

7. Expect delays

Any type of home repair seems to take longer than was first predicted. If the repairs involve any sort of interior demolition, expect divorce dust.

Emergency Funds

8. Have a contingency fund

Many home repairs end up unearthing something else that requires repair. While this is very common, ask lots of questions if your contractor is proposing additional work.

We trust that the above information will help people in their dealings with contractors, realign expectations, and perhaps avoid pitfalls.

Copyright 2015/2016 Carson, Dunlop & Associates Ltd.

All rights reserved

Priority Maintenance for Home Buyers

July 29th, 2016

Check list

Priority Maintenance for Home Buyers

There are so many home maintenance and repair items that are important; it can be confusing trying to establish which are the most critical. To simplify things, we have compiled a short list of our favorites. These are by no means all-inclusive, nor do they replace any of the information in a home inspection report. They should, however, help you get started on the right foot. Remember, any items marked as priority or safety issues on your home inspection report need immediate attention.


One-Time Tasks

1. Install smoke detectors as necessary (usually one on each level of the home, near any sleeping areas). Install carbon monoxide detectors, according to manufacturer’s recommendations.
2. Make any electrical improvements recommended in the home inspection report.
3. Remove any wood/soil contact to prevent rot and insect damage.
4. Change the locks on all doors. Use a dead bolt for better security and to minimize insurance costs.
5. Correct trip hazards such as broken or uneven walks and driveways, loose or torn carpet or uneven flooring.
6. Correct unsafe stairways and landings. (Railings missing, loose, too low, et cetera.)
7. Have all chimneys inspected before operating any of these appliances.
8. Locate and mark the shut-offs for the heating, electrical and plumbing systems.
9. Label the circuits in electrical panels.
10. If there is a septic system, have the tank pumped and inspected. If the house is on a private water supply (well), set up a regular testing procedure for checking water quality.


Regular Maintenance Items

11. Clean the gutters in the spring and fall.
12. Check for damaged roofing and flashing materials twice a year.
13. Cut back trees and shrubs from the house walls, roof and air conditioning system as needed.
14. Clean the tracks on horizontal sliding windows annually, and ensure the drain holes are clear.
15. Test ground fault circuit interrupters, carbon monoxide detectors and smoke detectors using the test button, monthly.
16. Service furnace or boiler yearly.
17. Check furnace filters, humidifiers and electronic air cleaners monthly.
18. Check the bathtub and shower caulking monthly and improve promptly as needed.
19. If you are in a climate where freezing occurs, shut off outdoor water faucets in the fall.
20. Check reversing mechanism on garage door opener monthly.
21. Check attics for evidence of leaks and condensation and make sure vents are not obstructed, at least twice a year. (Provide access into all attics and crawl spaces.)

Copyright 2015/2016 Carson, Dunlop & Associates Ltd.

All rights reserved