What is a Passive House? Terra-Petra Waterproofing Division

What is a Passive House?

The Passive House concept represents today’s highest energy standard with the promise of slashing the heating energy consumption of buildings by an amazing 90%. Widespread application of the Passive House design would have a dramatic impact on energy conservation. Data from the U.S. Energy Information Administration shows that buildings are responsible for 48% of greenhouse gas emissions annually and 76% of all electricity generated by U.S. power plants goes to supply the Building Sector [Architecture 2030]. It has been abundantly clear for some time that the building sector is a primary contributor of climate-changing pollutants, and the question is asked: How do we best square our building energy needs with those of our environment and of our pocketbook? In the realm of super energy efficiency, the Passive House presents an intriguing option for new and retrofit construction; in residential, commercial, and institutional projects.

A Passive House is a very well-insulated, virtually air-tight building that is primarily heated by passive solar gain and by internal gains from people, electrical equipment, etc. Energy losses are minimized. Any remaining heat demand is provided by an extremely small source. Avoidance of heat gain through shading and window orientation also helps to limit any cooling load, which is similarly minimized. An energy recovery ventilator provides a constant, balanced fresh air supply. The result is an impressive system that not only saves up to 90% of space heating costs, but also provides a uniquely terrific indoor air quality.

A Passive House is a comprehensive system. “Passive” describes well this system’s underlying receptivity and retention capacity. Working with natural resources, free solar energy is captured and applied efficiently, instead of relying predominantly on ‘active’ systems to bring a building to ‘zero’ energy. High performance triple-glazed windows, super-insulation, an airtight building shell, limitation of thermal bridging and balanced energy recovery ventilation make possible extraordinary reductions in energy use and carbon emission.

Today, many in the building sector have applied this concept to design, and build towards a carbon-neutral future. Over the last 10 years more than 15,000 buildings in Europe – from single and multifamily residences, to schools, factories and office buildings – have been designed and built or remodeled to the passive house standard. A great many of these have been extensively monitored by the Passive House Institute in Darmstadt, analyzing and verifying their performance. Even governmental agencies have adopted passive house standards in their policy-making (read more about the EU Commission’s intent to implement the Passive House Standard.).

Performance Characteristics

  • Airtight building shell ≤ 0.6 ACH @ 50 pascal pressure, measured by blower-door test.
  • Annual heat requirement ≤ 15 kWh/m2/year (4.75 kBtu/sf/yr)
  • Primary Energy ≤ 120 kWh/m2/year (38.1 kBtu/sf/yr)

In addition, the following are recommendations, varying with climate:

  • Window u-value ≤ 0.8 W/m2/K
  • Ventilation system with heat recovery with ≥ 75% efficiency with low electric consumption @ 0.45 Wh/m3
  • Thermal Bridge Free Construction ≤ 0.01 W/mK

What is a Passive House? Terra-Petra Waterproofing Division

The building science research culminated in the development of the Passive House Planning Package (PHPP) which projects detailed heat load, heat loss, and primary energy usage for individual building parameters. The latest version of the PHPP also projects cooling, cooling loads, and latent cooling. Based on feedback from many detailed data logged buildings, the software is constantly refined and incorporates updated calculations for various climates around the world.

Terra-Petra Waterproofing Division is available for you water management and consulting services.

Contact us for further information.

Bottom Line on Mold

Contributed by
Barry Taheri

According to the EPA, molds can be found almost anywhere -they can grow on virtually any organic substance, as long as moisture and oxygen are present. There are molds that can grow on wood, paper, carpet and insulation. When excessive moisture accumulates in buildings or on building materials, mold growth will often occur, particularly if the moisture problem remains undiscovered or unaddressed.

Molds produce allergens (substances that can cause allergic reactions), irritants, and in some cases, potentially toxic substances (mycotoxins). Inhaling or touching mold or mold spores may cause allergic reactions in sensitive individuals. Allergic responses include hay fever-type symptoms, such as sneezing, runny nose, red eyes, and skin rash (dermatitis).

Allergic reactions to mold are common. They can be immediate or delayed. Molds can also cause asthma attacks in people with asthma who are allergic to mold. In addition, mold exposure can irritate the eyes, skin, nose, throat, and lungs of both mold-allergic and non-allergic people.

Since mold requires water to grow, it is important to prevent moisture problems in buildings. Moisture problems can have many causes, including uncontrolled humidity. Some moisture problems in buildings have been linked to changes in building construction practices during the 1970s, 80s, and 90s.

In order to test the levels of mold in a particular structure, an air sample is taken of the entire structure area. The doors and windows must remain closed 24 hours prior to the test. Depending on the size, air samples are taken in three to four locations and on each floor. Tape samples are taken as well to determine surface contamination. An air sample is then taken outside the building and the two are compared. The results are then interpreted and repair and remediation protocols are developed.

Need to find concealed moisture before it’s a problem? Contact Terra-Petra to schedule a consultation.

 

Surface tension allows water droplets to cling to building surfaces, even downwards facing ones.

How Water Behaves

Contributed by Barry Taheri

Water has a simple molecular structure made up of two atoms of hydrogen and one atom of oxygen. In any single water molecule, the hydrogen atoms will have ‘spare’ electrons that can bond to the oxygen atom of other water molecules (this is known as hydrogen bonding). This bonding allows water molecules to form a liquid and influences the properties and behaviour of water, such as surface tension and capillary action.

  • Surface tension
  • Capillary action
  • Absorption and wicking
  • Condensation
  • Water from cleaning

Surface tension

When water molecules bond, those on the surface are pulled inwards by the hydrogen bond. This creates a kind of skin effect, called surface tension, which can be strong enough to resist gravity and allows droplets to cling to building surfaces.

In general, when a water droplet comes into contact with a hydrophobic material (such as gloss-painted weatherboards or glass), where there is no hydrogen bond between the water and the material, the water will tend to run off.

But when a droplet comes into contact with a hydrophilic material (such as uncoated concrete or unpainted timber), which absorbs water, surface tension will cause the droplet to flatten against and hold on to the material surface. The more the droplet flattens against the material, the greater its chance of resisting gravity and being held on the surface.

Water that is being held on building surfaces by surface tension will still drain down drainage paths on the vertical face of the cladding but may also drain from the vertical surface and cling onto an adjacent horizontal surfaces. Once it is clinging to a horizontal surfaces, it can be blown into a junction where it may penetrate and cause damage.

Creating a sharp transition to an upward slope or surface will make the water drip off at the junction. Surface tension therefore needs to be broken at all vertical to horizontal junctions. This is done with a drip edge, weathergroove, flashing or drip moulding.

Surface tension allows water droplets to cling to building surfaces, even downwards facing ones.

Surface tension allows water droplets to cling to building surfaces, even downwards facing ones.

 

 

 

 

 

 

 

Capillary action

Capillary Action WaterproofingCapillary action is where water bonding to two adjacent surfaces is drawn upwards against the force of gravity between the two surfaces. How far the water can be drawn upwards depends on the size of the gap between the surfaces and how hydrophobic or hydrophilic they are. Wind pressure can also act on the water and drive it upwards even further.

Incorporating a capillary break by detailing a gap of 6 mm between surfaces will stop capillary action occurring, as the surfaces will be too far apart for water to bond between them. The incorporation of weathergrooves, seals or hooks/seams on a flashing can also assist, as these will break the contact between the adjacent surfaces.  

Water wicking up a wall under a window.


 

 

 

 

 

 

 

Absorption and wicking

Absorbent or porous materials and surfaces (such as raw fibre-cement, uncoated concrete, weathered coatings and unpainted timber) will absorb moisture.

They can also wick moisture off an adjacent surface, where it can be absorbed. Once water has been absorbed, it will migrate or wick through the material from a warm area to a cold area. It may also be absorbed by other adjacent materials – for example, water may be absorbed by a poorly coated cladding and migrate through to be absorbed by a dry absorbent wall underlay and ultimately by the dry timber framing.

The use of non-absorbent materials or finishes will limit absorption, and the use of capillary breaks or a separation between surfaces (such as a gap at the bottom of the cladding above a waterproof deck) will restrict wicking.

Rapid heating by the sun of surfaces containing moisture can also drive water vapour from absorbed moisture through materials – a process known as solar-driven moisture transfer.

Rapid heating by the sun of surfaces containing moisture can also drive water vapour from absorbed moisture through materials – a process known as solar-driven moisture transfer.

 

Condensation

Air contains water vapour, with the amount of vapour present increasing with temperature. As air cools, its ability to hold water vapour is reduced, and the vapour is released and condenses as water. When air is cooled by contact with a cold surface, the released vapour forms as condensation on that surface (for example, the steam created from a hot shower will condense when it comes into contact with the cooler glass of an exterior window).

If condensation occurs, it can be absorbed by materials and can cause material deterioration, so it needs to be managed within wall assemblies. This can be done by ventilation and by incorporating absorbent wall underlays or using cladding materials that have some degree of absorbency on the back of the cladding that will hold the condensation water until it dries again as a result of ventilation.

 

Water from cleaning

Building exteriors should only be cleaned with very low-pressure water (less pressure that a water hose), as high-pressure water (such as that from water blasting or a high-pressure hose) has the potential to be directed at and driven through gaps in the exterior cladding and up under flashings, where it can enter the roof or wall assembly and be absorbed by components.

High-pressure water can also damage softer cladding materials and damage or remove protective exterior coatings

If you have any questions or concerns please contact us.

Waterproofing Options for Concrete Foundations

Contributed by Barry Taheri

Problems Caused by a Leaky Foundation

“Do it right the first time.” It’s almost a cliche. But when it comes to waterproofing concrete, not doing it right the first time can have truly disastrous results. A leaky foundation in a residential building can damage finishes and furnishings, even the structure itself. In a commercial building, water can ruin expensive equipment and disrupt vital work. It all adds up to lost money, wasted time, upset customers and sometimes litigation.

The Problem with Damp-Proofing… It Won’t Stop Water Bearing Against the Foundation

Waterproofing isn’t pretty, and since it’s going to get buried anyway, it’s easy to skimp and go for damp-proofing instead, painting on that old black stuff that comes in a bucket. But damp-proofing will only retard moisture; it can’t stop a head of water bearing against the foundation.

Nearly all waterproofing products can be applied to concrete block as well as poured concrete walls, and most of the same concerns and practical tips are relevant.

Choosing Waterproofing Concrete Products

There are many below-grade waterproofing products on the market. Most manufacturers require you to become a certified applicator before they will guarantee an installation. If you’re just going to do occasional waterproofing, I suggest you choose one product, get certified by the manufacturer, and learn all about that one product. Eventually you’ll get good at applying it and be able to work quickly and safely. Different products can have very different characteristics, so only specialty waterproofing contractors should try working with multiple products.

Because there are so many materials on the market, any waterproofing job should begin with a careful review of the manufacturer’s literature, maybe a phone call to a technical service representative, and possibly even a site visit by a field representative.

Liquid Membranes

You apply a liquid membrane by spray, roller, or trowel. The liquid cures into a rubbery coating on the wall. One manufacturer has a spray-applied liquid membrane composed of polymer-modified asphalt. Polyurethane liquid membranes in separate grades for trowel, roller, or spray are also available from various manufacturers.

Watch application procedures carefully.

The manufacturer probably has a special procedure for treating voids, form-tie holes, and joints. At the wall-footing joint, you may be required to use cement or other trowel-grade material to form a “fillet” (radius or cove) before applying the overall coating.

Liquid coatings have the advantages of quick application, low in-place cost, and excellent elongation. One of the chief disadvantages is the possible inconsistency in coverage. The typical application thickness is 60 mils, but it takes a careful applicator to be sure of always achieving that minimum coverage.

Sheet Membranes

The most commonly specified sheet materials are self-adhering rubberized asphalt membranes. These 60-mil-thick membranes are composed of rubberized asphalt laminated to a waterproof polyethylene film. The asphalt side is incredibly sticky but is covered by a release paper, which you remove during application.

The first time you work with this material, it’ll drive you crazy because it sticks to everything. But you’ll be surprised how fast you can move with it once you develop a rhythm. It takes two people, one on top to smooth it out and stick it down, the other on the bottom to pull off the paper. You’ll have many details to learn about surface preparation, priming, patching, joint treatment, terminations, lap joints, penetrations, and corners.

Because they’re so sticky, these membranes can be pretty unforgiving. Once a piece is down, you won’t get it back up again at least not in reusable condition. However, the system allows easy repairs of holes, fishmouths, puckers, and wrinkles. You’ll patch holes or damaged areas with a piece of membrane placed right over the first layer. With a fish-mouth or wrinkle, all you do is slit the raised area, press it down flat, and cover it with a patch.

A chief advantage of sheet membranes is their consistent thickness. Because they’re manufactured to exacting tolerances, you can be sure of the 60-mil coverage. These membranes also have good elongation.

A higher in-place cost is one of the main disadvantages of sheets. The cost of the material itself is likely to be greater on a square-foot basis than the liquid membranes. Labor cost is also higher, because of all the cutting, handling, reinforcing, and detailing you have to go through during installation.

Not everyone agrees, however, that sheet membranes lessen the quality-control risk. A rubberized liquid forms a continuous, seamless coating, whereas a sheet membrane results in many seams, with the potential for a poor seal. If you’re applying these materials, make sure your lap joints are tight and properly detailed. Make correct use of the manufacturers mastic or other accessories. For example, one manufacturer requires you to apply a bead of mastic to every lap joint within 12 inches of a corner when using its product.

Cementitious Waterproofing

Cementitious products are probably the easiest waterproofing materials to use. They’re readily available from suppliers of masonry products, and they’re easy to mix and apply. If you plan to use this material, a long-handled brush will make your life easier. Also, spend the extra money to buy acrylic additive (a white, milky liquid) to mix in with the cement product. You’ll get better bonding and a more solid, durable coating.

The chief disadvantage is that cementitious products have no give to them probably because cement just doesn’t stretch to any degree worth mentioning. They will stand up fine to a head of water, but will tolerate almost no joint or crack movement.

Concrete Waterproofing Built-up Systems

When I first went into the waterproofing business, I did a number of jobs with a hot-mopped, asphalt-and-felt built-up system. With these systems, you first apply a concrete primer. You then mop on a coating of hot tar (which is heated in a large asphalt kettle), followed immediately by application of a sheet of perforated felt, extending the system right out onto the footing. You keep staggering the felt sheets until you have three layers of felt with a final coating of tar. (The local building code may let you get by with only two plies.)

This is a good system with a lot of strength, but probably not much elongation ability. You can produce a similar built-up waterproofing system using cold, trowel-grade dampproofing and reinforcing fabric. Again, this system has some strength but little elasticity.

Bentonite

Sodium bentonite, a clay material, has enjoyed a steady upsurge in popularity over the past several years. In panel form, bentonite has become the choice of a growing number of architects and builders. Bentonite works because it can absorb a tremendous amount of water. As it takes in water, the clay swells to 15 times its original volume and pushes itself into cracks and voids. When it reaches its maximum volume, it stays in these areas permanently to seal against water. One firms panels are 4×4-foot corrugated cardboard with clay particles held within the flutes of the cardboard. The panels can be nailed, fastened with a powder-actuated tool, or simply laid in place for horizontal applications.

Some waterproofers are nervous about using bentonite panels. With other products, you can inspect the finished waterproofing application and confirm the integrity of the seal before backfilling. With bentonite panels, the seal doesn’t form until the foundation is backfilled and water reaches the panel. Suppose something goes wrong? It’s a nagging question for “traditional” waterproofers.

Bentonite has its advantages, however: It’s safe to work with, non-polluting, easy and quick to apply, and can go on even at low temperatures. One company makes a sheet membrane that uses a compound of bentonite and butyl rubber.

Surface Preparation

Don’t skimp on surface preparation. You must get the foundation wall and footing clean, free of loose material, and fairly smooth. Do as much as you can ahead of time: Once you start waterproofing, rhythm is crucial, and you don’t want to have to stop to scrape loose concrete from the footing or break off a form tie.

Waterproofing materials aren’t designed to cover large voids or honeycombs. You’ll need to fill these, preferably with nonshrink grout or a good patching cement. You may be able to patch form-tie holes or smaller voids with trowel-grade mastic. Check the manufacturers instructions to make sure that whatever material you use for patching is compatible with the waterproofing product.

Surface Preparation Procedure

Waterproofing likes a clean wall. Here’s what I recommend for a surface preparation procedure:

Survey the entire surface to be waterproofed. Identify special problems, such as water on footings, concrete forms not removed, footings not dugout, and pipe penetrations not prepared. Have these problems worked on right away, especially if these areas are the responsibility of another trade.

Dry off all footings. A big propane torch with a 20-pound tank is good for this. For puddles, sweep standing water off with a broom, then dry the damp spot with the torch.

Remove concrete form ties. If there’s an odd form tie that wasn’t aligned properly and won’t break off flush, cut it off with a cutting torch or reciprocating saw. Break form ties off on the inside of the foundation too. Another waterproofer once told me that on one of his jobs the general contractor sent in a laborer, after waterproofing was applied, to break off form ties on the inside of a foundation. The laborer decided it would be easier to just pound the ties back into the wall. Every one of them punched through the waterproofing membrane on the other side, which was already backfilled.

Scrape off excess and loose material from walls and footings. A long-handled ice breaker is good for this. Some waterproofing manufacturers will require you to machine-grind any ridges or protrusions before applying their products. It’s good to have a brick hammer on hand, too. Pay special attention to the footing. Quite often, puddles of congealed slurry form on the footing when the wall is poured. This material doesn’t have the full strength of concrete, it isn’t bonded to the footing, and should scrape off easily.

Sweep off the walls and especially the footings. They don’t have to be clean enough to eat off of, but don’t leave a film of dust or mud. Waterproofing materials won’t stick to a dirty surface. Keep other trades and workers out of the area. Besides the safety hazards, other workers tend to be oblivious to what waterproofers are trying to accomplish. Many times I’ve cleaned a footing, only to see a muddy-booted laborer stride right down its length, leaving tracks the whole way.

Take care of any patching or filling. Grout around penetrations and follow any other instructions from the waterproofing manufacturer that apply at this point.

Scheduling and Planning For Concrete Waterproofing

Allow considerable float time for waterproofing. If you’re using a waterproofing subcontractor, recognize that good waterproofers can be in high demand during the busy season. Rain can also delay waterproofing work.

Plan the layout of waterproofing well ahead of time. The plan elevations will likely show the finish grade line on the foundation walls, but these lines should be confirmed with the architect, if necessary.

You don’t want black, gooey waterproofing showing above grade. Watch for changes in the level of grade. A line of waterproofing descending at a diagonal from one level to another won’t work if the architect has decided to handle the change with a retaining wall.

Construction Tips

Ideally, you should mark layout lines with a crayon or chalk line, especially on a complex foundation with varying grade. On a simple foundation, it might be safe to just instruct the waterproofer to keep his work so many inches from the top of the foundation. I like to see waterproofing as close to finish grade as possible, but no lower than 6 inches in any case. Don’t leave form-tie holes that are below grade unprotected. Work out ahead of time what you’re going to do at basement windows and bulkheads, porch foundations, and intersecting walls that don’t have to be waterproofed.

When deciding what walls get waterproofed, follow this basic rule: Waterproof any foundation wall that has earth on one side and usable space on the other, including crawl spaces. Extend waterproofing at least 12 inches onto intersecting walls that don’t have to be waterproofed. You might want to continue the waterproofing on other walls if it’s a very wet site. Under extreme conditions, water has been known to travel through the keyway along the footing and into occupied space. Consult with the architect if you have any doubts.

Check the waterproofing manufacturers literature for temperature limitations. You’re probably okay applying waterproofing on a cold day if you’re working with a solvent-based material. But watch out if your material is water-based. The lower limit for some products is 40F.

Waterproofing Curing Time

Likewise, check the manufacturers requirements for concrete curing time. For every sheet membrane I know of, concrete must be cured a minimum of seven days before membrane application, sometimes even longer. This is because the concrete will continue to dry long after it’s poured. The water vapor escaping from the concrete can prevent the waterproofing material from bonding. Concrete curing times for liquid membranes also vary considerably. Some require 14 days or longer. Others can be applied as soon as the forms are removed.

Protecting In-place Waterproofing

Most waterproofing systems need protection during backfilling. Some manufacturers have their own protection board for this purpose. A drainage mat or insulation can also function as protection board. An inexpensive 1-inch-thick expanded-polystyrene-foam board works fine as a basic protection course. However, one manufacturer has a protection board that functions as insulation, protection board, and drainage medium in one.

When adhering protection board, make sure to use an adhesive that’s compatible with the waterproofing membrane. I’ve seen some adhesives eat right through waterproofing material. Besides providing protection during backfilling, you should protect waterproofing work that is in place from damage by other workers and trades. Keep workers from tracking across exposed membranes on footings, decks, or other horizontal surfaces. Don’t expect others to be as sensitive as you are to the importance of waterproofing.

Don’t Neglect Drainage When Waterproofing

No waterproofing system I know of is designed to work without proper drainage. Without relief, water can build up tremendous pressure underground. A waterproofing manufacturer won’t warrant its product if drainage is missing or inadequate, or if the structure is built on a site where proper drainage is impossible.

The minimum drainage for any building is a perimeter footing drain. Depending on conditions, some buildings will require an underdrain system or a sump pit with a pump.

Waterproofing Safety

Waterproofing below grade can be dangerous. Because of the hazards, it’s usually not a good idea for anyone to waterproof alone. If you’re using a water-proofing subcontractor, make sure workers follow a written safety program and comply with hazard-communication requirements. Keep other trades and workers well away from the waterproofers work area.

Once you learn how to work with waterproofing materials, you can make good time without sacrificing safety. Here are some primary safety concerns that go along with waterproofing.

Flammable materials: Many waterproofing products are solvent-based. Keep fire, smoking materials, welding operations, cutting torches, and other sources of ignition well away from the area.

Respiration hazards: Use the manufacturer-recommended respirator, especially with solvent-based materials. In a close area, you might need an air-fed respirator. Don’t be complacent about this. Solvent vapors are deadly, and a large surface area of newly applied material can put out a lot of vapor. The vapors are usually heavier than air, so they tend to build up in a sunken area like a foundation excavation.

Skin injuries: Waterproofing materials can contain all sorts of chemicals that can harm your skin. As needed, wear protective clothing and gloves. When cleaning tools in solvent, wear chemical-resistant gloves.

Injection hazards: Take precautions when working with or around spray equipment. A high-pressure airless sprayer can inject toxic chemicals directly into your blood-stream.

Eye injuries: Wear protective glasses or goggles as needed, especially when working with liquids.

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If you should have further questions, do not hesitate to contact Barry Taheri or call our office.