+ Was ist das passivhaus?

Since its inception in 1991, the passivhaus (passive house) design standard has gained international prominence in the building sector.

The passivhaus standard is the world’s leading building standard for energy efficiency. A building constructed to the passivhaus standard will consume 90% less heating and cooling energy and 80% less total energy when compared to the typical building stock.

It’s also a standard for comfort. Passivhaus design eliminates cold spots, draughts and overheating as well as provides a constant supply of clean and fresh air. It is the only building standard to exceed the EPA’s requirement for indoor air quality.

A passivhaus captures solar heat through properly oriented and high-performance fenestration systems and retains this heat through a super-insulated building envelope.

We enjoy this short video, “Passive House Explained in 90 Seconds” by Hans-Jörn Eich.

+ U-value vs R-value

Both U-value and R-value are measures of energy efficiency. However, they measure energy efficiency differently. The thermal performance of windows is defined by U-value. The thermal performance of uniform materials (e.g., insulation, wood, drywall, and concrete) is defined by R-value.

U-value refers to the measure of heat transfer (heat gain or loss) through a building component. U-value is not a material property; it is a calculation of the thermal transfer properties of the individual components in a window or door system. A lower U-value is preferable and will result in better thermal performance of a window system and require fewer energy inputs in conditioning the living space. The overall U-value of a window is a function of the U-value of the IGU and the U-value of the frame. That is why we use thermally-broken aluminum and steel frames and a high-insulating layer in our highest-performing wood frames.

R-value is a measure of the resistance of a material to transfer heat. This is a material property. A higher R-value denotes better thermal insulating properties. In the international system of units (SI), U-value is expressed as watts per square meter-kelvin [W/(m2⋅K)]. U-values for European windows are specified in SI units. In the US, U-value is expressed as British thermal units (Btu) per hour-square feet-degrees Fahrenheit [Btu/(h⋅ft2⋅°F)]. To convert from SI to US customary values, divide the SI U-value by 5.678.

Furthermore, R-value is the inverse of U-value. That is R-value = 1/U-value. For example, a window with a U-value of 0.3 has an R-value of 3.3; a window with a U-value of 0.1 has an R-value of 10. This is true as long as the same system of units (i.e., SI or imperial) are used for both U-value and R-value.

In Europe, the U-value of glazing (Ug) is calculated in accordance with EN 673.

+ What's an IGU?

Glazing is the industry term for glass. The assembly of the multiple glazing panes and spacers is called an insulated glazing unit (IGU). The composition and construction of the IGU are just as important as that of the frame.

Generally speaking, the more panes of glazing (i.e. double, triple, or quad), the more your conditioned space is protected from the outside environment. But there's more to it than simply the number of panes. It's also important to properly space the panes and this is why we utilize the highest quality warm-edge Swiss-made spacers.

It is most common to space the panes evenly within an IGU. However, the panes can be spaced differently for sound abatement. IGUs can also consist of ESG (Einscheiben-Sicherheitsglas) also known as tempered glass and VSG (Verbundsicherheitsglas) also known as laminated. These unique assemblies have unique properties. Our glazing units are tailored specifically to your project and even to each glazing unit within that project.

+ What's the E in Low-E?

e·mis·sive | əˈmisiv | adjective technical having the power to radiate something, especially light, heat, or radiation.

Low-E, or Low-Emissivity, coatings are microscopically thin coatings applied to glass in order to alter the performance of the IGU. Low-E coatings affect the transmission of infrared (IR) and/or ultraviolet (UV) light while allowing visible light to pass. Some Low-E coatings also affect the Solar Heat Gain Coefficient of the glazing. These coatings are applied to the interior (chamber side) of the glass panes within the glazing unit. And they can result in different effects depending on which surface of which pane they are applied.

In general, IR light passing through glass results in the heating of an interior space, while UV light can affect fading of floors and fabrics. Depending on the design intent, geographic location, and site orientation of the individual glazings, different coatings can be specified to optimize solar gain where needed and minimize overheating where it is not. This is especially critical in the design and function of Passivhaus structures and other high-performance, low-energy homes and buildings. There is no one-size-fits-all approach to specifying Low-E coatings. We will work with you in the design process to help select the proper properties of the IGUs.

+ SHGC

The Solar Heat Gain Coefficient (SHGC) is a measure of the permeability of total solar radiation energy through a glazing unit. It is stated as a percentage, expressed as a number between 0 and 1. The lower the number, the less solar energy is transmitted and the greater the shading ability of the glazing. For example, if you live in a predominantly cooling climate (e.g., Miami) you would specify glazing a very low SHGC. However, if you live in a predominantly heating climate (e.g., Minneapolis) you would likely desire glazing with a higher SHGC. Additionally, the orientation of the glazing (i.e., north, south, east, and west) can influence the desired SHGC. Low-E coatings are responsible for affecting the SHGC of a glazing unit. Again, we will help you optimize your glazing package based on your site-specific needs.

+ How important is the installation process?

Proper installation of Vonderhaus fenestration systems is paramount to ensure maximum energy efficiency, airtightness and smooth operation. This cannot be overstated. We will refer one of our approved installers for optimal performance of your system.

Additionally, we recognize there are various ways in which our systems will integrate with interior and exterior finish surfaces. These variations should be accounted for early in the design phase. We encourage a collaborative approach in advance of the framing process in working toward realizing the design idea. We can advise on integration with design details, air sealing details, rough opening requirements, and can consult on unloading, storage and handling procedures. Let’s work together to ensure a smooth and seamless installation.

+ Should I take my geographic location into account when choosing my system?

Indeed. We will consult with you on which system performs best with your climate. For instance, projects located above 2,600 feet (apprx. 800m) require a pressure regulation system and treated glass. Also, contingent upon the orientation of your project, we will consult on how much solar heat gain you would like to capture (see Solar Heat Gain Coefficient below).

+ What about the birds?

Researchers estimate that a billion birds are killed each year due to collisions with glass in buildings, making bird collisions one of the most significant causes of avian mortality globally. We like birds and that is why we offer a patterned, UV reflective coating that makes the glass visible to birds while remaining virtually transparent to the human eye.

+ What's all that noise?!

We agree with Sir Edward Coke who declared a man's house is his castle. We interpret this slightly differently than Coke intended, but all the same...we believe it. While residing in a densely populated urban setting is invigorating and environmentally beneficial, we understand the need for some to create a place of refuge - the ability to escape the hustle and bustle and allow oneself to decompress. This is why we offer systems with superior sound abatement properties.

Glass is separated into five sound reduction classes according to the Deutsches Institut für Normung (DIN). DIN is the German Institute for standardization and a member body of the International Organization for Standardization (ISO). The ISO 140 is concerned with field measurements of airborne sound insulation and impact sound insulation and uses the Weighted Sound Reduction Index (Rw) to denote sound classes. We can provide glazing units in any of those five DIN classes with differing Rw values to meet specific sound reduction requirements.

What about Sound Transmission Class (STC)? Rw covers a larger frequency range than STC. Additionally, Rw corresponds to the decibel scale and is a number used to rate the effectiveness of a soundproofing system or material. Increasing the Rw by 1 translates to a reduction of approximately 1db in noise level. Therefore, the higher the Rw number, the better a sound insulator it will be. STC values are around 3-4 dB higher for the equivalent sound insulation than Rw. (47dB STC = 44dB Rw).

The five classes according to DIN:

Approximate noise level generated by:

For example, if the noise level outside is 90 dB (i.e., traffic) and you want the noise in the interior space to be in the range of a quiet home or light office (40-50 dB), Class 4 glass with an Rw of 44 should be used: 90 dB - 44 dB = 46 dB.

+ Thermal Insulation...Explained.

Insulation is the property of any material that obstructs the flow of heat through it. In warm climates, insulation serves to reduce the heat entering the building, and in cold climates, to reduce the heat that escapes.

The thermal conductance (the ability to allow heat to pass through it) of any material, K, is measured in Watts / m²Kelvin, in metric units, for a given thickness of that material.

This means that if the thermal conductance of a slab of material 10 cm thick is 1 W/m2.K, then 1 Watt of heat will flow across one square meter of that slab if the difference in temperatures on the two sides of the slab is 1 degree Kelvin. One degree Kelvin is the same as one degree Centigrade. If the difference in temperature of the two sides is 10°C, (for example if the temperature outside is 35°C and inside, in a conditioned office, it is 25°C), then 10 W of heat will flow across our slab.

R VALUE, K VALUE AND U VALUE EXPLAINED

The R-value, which is the thermal resistance of any material, is the inverse of the K-value. That is, R = 1 / K.

So if we have a material whose K value is 4 W/m²K,

its R-value will be 1 / 4 = 0.25 m²K/W

We must note that so far we have been dealing with European S.I. (metric) units. However, Americans use BTUs per hour instead of Watts (a BTU is a British Thermal Unit), square feet instead of square meters, and degrees Fahrenheit instead of Centigrade or Kelvin. So their unit for R-value is hr-ft2-°F/Btu.

Now 1 m²K/W = 5.678 hr-ft²-°F/Btu

So, to convert from the SI R-value to the American R-value, multiply by 5.678.

Let us return to the slab we were previously discussing. If we now double the thickness of our slab to 20 cm, the amount of heat entering will halve. This is because the R-value is directly proportional to the thickness of the material. So when we speak of R-value, we are always referring to the R-value of a specific thickness of that material. If we do not mention the thickness, then we mean the R-value for a slab of that material is 1" thick.

So if we see from a table that the R-value of a brick wall is 0.2, then we should understand that the R-value of a brick wall 1" thick is 0.2 hr-ft2-°F/Btu. We can then calculate that the R-value of a 4" thick brick wall is 0.8, and of an 8" thick brick wall is 1.6.