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Passive House Design: Insulation–That’s a Wrap

This is the third post in our series on Passive House Design. If you missed either of the previous, click on the links below to get up to speed! LEAP’s intelligent design process consists of four main steps, each building on the previous. Site analysis is the first step, because it informs all the other steps. You can have all of the best windows, doors, and insulation, but their effectiveness is diminished if the orientation of the structure isn’t correct.

Passive House Design Process

Today we explore the importance of insulation, and avoidance of thermal bridging.

Site Analysis
Doors and Windows
Insulation
Air Sealing

Insulation to Minimize Heat Loss

A typical modern house loses and gains approximately 150 kWh/m²a of heat, where the units refer to energy per floor area. A “leaky house” will have double those losses — think older windows, no wall insulation, and degraded door seals. On the other hand, a passive house will be 20x more efficient compared to the leaky house, and 10x more than a typical modern house. A big part of how Passive House Design minimizes thermal gains and losses is through super insulation.

passive house insulation, passive house design

Comparison of heat gains and losses for different house types.

Passive House Standards

Per the definition of Passive House—it can use no more than 1.4 kWh per 1 ft² of living space annually. For example, a 2,000 ft² house would only use 2,800 kWh per year, which comes out to $280/yr (@ 10 cents/kWh). To achieve this efficiency, we’ve discussed how the structure’s envelop must be air-tight, but we also need to insulate the heck out of it.

The insulation itself is generally comprised of multiple layers, all with high R-values. This insulation covers the entire envelope of the structure, including under the footing,with the only exception being the windows and doors. To be continuous, the insulation goes on the outside of the framing, opposed to between studs in a conventional building. The outermost layer of the insulation-sandwich is a water/wind membrane, which tends to be UV sensitive. This necessitates installing siding to cover and protect the membrane.

This configuration significantly reduces the heat transfer through the walls, roof and floor compared to conventional buildings. A wide range of thermal insulation materials can be combined to provide the required high R-values. Special attention is also given to eliminating thermal bridges.

A thermal bridge is a break in the insulation surrounding the house. In a traditional home, this would include all framing members of the structure, and things like porches and overhangs. Thermal bridges lead to massive heat loss, negating the benefit of “over insulating” the structure.

Example of a possible combination of insulation layers for a Passive House Design.

Much Ado About Porches, Decks, and Overhangs

We don’t pay special attention to these “add-ons” for nothing. There are lurking thermal bridges…ready to let all the heat in (or out) of our carefully crafted structure. So instead of penalizing Passive House structures and sending them to the corner with no porches or decks, we work around it. Normally a ledger board would be affixed to the structure as a supporting member for the deck or porch. Instead, we design it to stand-off, and put all of our support posts in the ground. In this manner, we avoid creating a break in the continuous insulation wrap.

So to wrap up, (pun intended), think of super insulation for a passive house like Ralphie’s brother in a Christmas Story. He is bundled to the max, layer upon layer of winter clothes, along with socks, boots, gloves, and his hood pulled so tight that he can barely see—and all on the outside of his “frame”. I guess Randy and Ralphies’ mother understood the dangers of heat loss and thermal bridging back in the 50’s. That lady was well ahead of her time.

[box type=”bio”] Interested in Passive House or Green Building Design? Whether you want to start from scratch or renovate—we can help! Every $1 spent on design saves $10 in construction costs. Don’t shoot your eye out. Let us provide you the best design possible. Contact us to get started.[/box]

Passive House Design: Windows— A Dark Age Salvation

in Passive House Design, Stories

We are continuing our series on Passive House Design. LEAP’s intelligent design process consists of four main steps, each with the aim to maximize human comfort, energy efficiency, and real cost savings. Today we explore the importance of good windows and doors, along with what constitutes them as such.

Passive House Design Process

Site Analysis
Doors and Windows
Insulation
Air Sealing

We Aren’t Living in the Dark Ages, or Are We?

So you took a perfectly good, well insulated structure and put holes in it. Oops, I mean windows. You put windows in. But that’s one of the reasons we crawled out of caves and stopped living like mole-people. Our homes and offices are more pleasant with natural light and vitamin D.

Let’s look at an example somewhere between mole-people era and modern times—the reign of castles. I think we can agree that castles were not the pinnacle of energy efficiency. To support this claim, Eric “Outlander” Davenport, traveled back in time to report the effective R-values of castles as 4… Well, in comparison, the effective R-value of a passive house is 42. (Well really it’s 40, but we all know the answer to life, universe and everything is 42).

So what the heck is this effective R-value you speak of?

R-value stands for resistance to heat flow. The higher the R-value, the greater the insulating value.

Effective R-values are the TOTAL resistances provided by all components in a wall assembly. This equates to patience and higher math—tallying up the thermal bridging, air infiltration, radiant heat loss or gain, and moisture impact on the overall structure. These factors usually reduce the effectiveness of the labeled R-value, on say conventional cavity-filled insulation.

Poor window quality can totally tank your whole effective R-value. You can construct your walls from the most insulating material in the world, but if you’re then installing crap windows, you might as well tack an oil cloth over the opening and call it good.

Which brings us to the puffy sleeves of the 1980’s. Building designers deemed “Windows for all” & “Architecture is above human whims!”, as a backlash to the 1970’s energy crisis and inoperable windows. This equated to: we can put windows everywhere, (even on the—gasp—west side of the building) and a window, is a window, is a window. We shall install the same windows in New York, California, and Alaska—climate dependence be dammed!

Well, to give you an idea of how well that worked out—the one design fits all approach—the effective R-value of these buildings dropped back to 4. Yes, 4. Your new, beautiful, big-hair building is the energy equivalent of living in a drafty castle. Back to the dark ages. (Weren’t puffy sleeves popular in the middle ages too? Coincidence?)

So we continue to claw our way out of the dark days of the 80’s, towards the light of Passive House Design. Good windows (and doors) equals a good thermal envelope, which equals a high effective R-value (42!), which spreads comfort and energy efficiency across the land.

What Constitutes a High Efficiency Window?

Soft, but what light through yonder window breaks? It faces east, and 2″ is the notch. Or rather, placement and construction—a high efficiency window doth make. And who pray tell constructs the finest windows in the land? Well, the Europeans do. Perhaps it was those long, drafty years of castle living that haunt their collective consciousness. But at any rate, they have figured out how to build a great window. And the big secret? A deep notch.

A deep notch accomplishes two things: makes the structure stronger, and reduces thermal bridging. The wood/glass interface is the weakest part of the window, and also where most of the energy is lost. European windows have a 2″ notch, whereas most American made windows are only 1/2″. This extra 1.5″ seats the glass securely in the frame and significantly reduces air leakage.

The Passive House Institute has a database of Passive House Certified windows and doors (and no, they don’t have to be European). When manufacturers from anywhere meet Passive House specifications, they can become certified. Below is an example of what a Passive House Institute certification seal looks like. Notice the list of 7 different climate regions.

Types of Windows

The type of window is also important. Double hung are out. Casement, awning, and fixed windows are in. Tilt-turn windows are a good option for functionality and air sealing, see image below. The three positions (fixed, tilt, turn) allow for security, venting and ease of cleaning, respectively.

Placement is another key factor. For balanced daylighting, large and floor to ceiling windows are typically placed on south and east facing walls. Small windows are placed high up on the north facing wall. As a rule of thumb, window area is no more than 10% of the total floor area for a given room. This helps prevent overheating in the summer and losing heat in the winter.

3-Tilt-Turn-Windows-passive house design

Tilt Turn Windows are a good choice for Passive House Design. Image from Glo Windows.

We didn’t really touch much on doors, but the same principles apply: good sturdy frames and good sealing will be more energy efficient. Bad doors are like installing a portcullis? It’ll keep the critters out, but not much else. The payback for spending a little more money upfront on good doors and windows is well worth it. Want to know how much? Contact LEAP Architecture today, and we can fill you in!

Passive House Design: Live like Goldilocks, Minus the Bears

in Passive House Design, Stories

Designing by trial and error can be exhausting. Take it from Goldilocks. She was so tired after all the rigmarole of finding “just right”, she actually fell asleep in a bear’s house. LEAP Architecture takes the guess-work out of Passive House Design with our (Bear-Proof) Design Process. Our intelligent site design consists of four main steps, each with the aim to maximize human comfort, energy efficiency, and real cost savings.

Passive House Design Process

Site Analysis
Doors and Windows
Insulation
Air Sealing

This week, we focus on the in’s and out’s of site analysis. We circumvent all the wandering through the woods, sleeping on hard beds, and eating loads of porridge. We nail just-right the first time around. Did we mention it also provides a great payback?

Proper Planning Prevents Piss Poor Performance

That old military adage couldn’t be more appropriate here. Maybe we’ll make it the company tagline. But seriously, upfront site planning for your building makes so much sense. And, it doesn’t cost anything extra! The builders don’t care if your front door faces north or south, but when the arctic air blows in, you will. It pays to orient the building to capture more sun-heat in the winter and stay cool in the summer. Here’s how we figure it out.

The Down and Dirty of Passive House Design

We measure, map out and consider all of the following:

Sun paths—Measure and diagram the arc throughout the year, location of shadows
Wind patterns—Measure and map the micro and macro climates
Vegetation— Survey what, where, tall/short, do they break wind? (hehe, break wind)
Topography—Hills? Valleys? (Caves of hibernating bears?)
Roads—The approach. You would like to access your building, wouldn’t you?
Views—Gaze on lavender fields doing dishes (move to France, but you get the idea)
Notoriety or Privacy?—To be seen or not to be seen, that is one of many questions.
Acoustics— Want to hear the babbling brook, but not the highway?

We combine your personal preferences with the climate data to optimize the placement of your structure.

Geometry: Be There or Be Square—if You’re a House

Building geometry is defined by how large your structure is going to be, or it’s volume. Smaller structures, like houses, are more efficient with a square footprint and minimum surface area. If you are not a house, be rectangular. High surface area buildings are much better for offices and larger structures.

To help understand surface area, picture a cube vs. a long rectangle. They can both have the same volume, but the cube is more compact, where the rectangle is long and skinny. The actual surface exposed to the outside environment for the cube is smaller, requiring fewer square feet of insulation. Smaller structures tend to be externally loaded, which means the outside environment has the largest influence on its energy efficiency. Minimizing the area for that interaction to take place helps to dampen the effects.

A higher surface area to volume ratio is desirable for larger structures, as they tend to be internally loaded—meaning inside activities have the greatest influence on the inside environment. Picture a skyscraper—the sheer number of people occupying the building, machinery running and other inside activities have a much greater impact than the outside environment. A rectangular structure is preferred (vertical or horizontal), not only for the higher surface area, but to also help maximize natural light penetration into the space. Ample natural lighting can significantly reduce electricity usage.

Quick Summary of Building Geometry:

Smaller structures:

Maximize building volume; minimize surface area
Square floor plan preferred
Tend to be externally loaded structures- outside activity effect environment

Larger structures:

Higher surface area than volume is desired
Rectangular floor plan is optimal
Better for natural light penetration
Internally loaded structure -inside activity effects environment

Orientation – Get your Walls on Straight

All that previous work of mapping the sun and wind and rain and…well, that gets put to work. Houses for example, will predominately have windows and doors located on south and east facing walls. This helps reduce blasts of arctic wind infiltrating your domicile, as cold wind tends to blow from the north in the north east. Eric Davenport, our very own Avatar, also considers things like banking wind currents off hills to create more ventilation in your house. If this isn’t some air-bender shit, I don’t know what is.

For larger structures, orienting the short end of the rectangle to face west will prevent that terrible afternoon glare on your computer screen and eyeballs. Maybe you’ve experienced this unfortunate office situation, or another. When the long side of the building faces west —the afternoon sun heats 1/2 of the building, jacking that side up to 90 deg—and those people get hot. People on the dark side freeze because the air conditioning kicked on and now their space is 50 deg. Intelligent site design gets the temperature in your office building just right, keeping the bears happy and solving all your HR issues. Well, at least the fight over the thermostat.

[box type=”bio”] LEAP Architecture Makes Environments JUST RIGHT!

Passive House: High Performance Construction Standards in the US

in Passive House Design, Stories

Passive House Design [founded in the US, then developed in Germany as Passivhaus] is different than passive solar design since insulation and heat exchangers are utilized while solar energy plays a lesser role.

Passive House Design: Introduction and History

In the United States, passive house design standards dictate space heating energy of 1 BTU per square foot (11 kJ/m²) per heating degree day which equates to 75-95% less energy for space heating and cooling than current new buildings that meet today’s US energy efficiency codes. [1] Typical strategies implemented to achieve the standard include well insulated envelopes coupled with air barriers, air sealing, and the use of heat exchangers to recirculate indoor air. Other considerations include: passive solar design, landscape design, advanced window technology, airtightness, ventilation, space heating from internal heat sources such as equipment and people, lighting and appliance efficiency.

Passive Building Attributes

Advantages of passive buildings include fresh, clean air, homogeneous interior temperature, slow temperature changes, and low energy loads that support renewable energy sources. Passive buildings could be up to 14% more expensive upfront than conventional buildings. [2] However, when designed to balance budgets, the mechanical system costs and alternative energy system costs are reduced. These reductions in system costs off-set the money spent on better insulation, windows and doors. And, owners get the payback dollars for insulation, windows and doors permanently in the building, as opposed to spending money on replacing mechanical and alternative energy systems 13-15 years down the road (just as they started getting pay-back!).

Passive House Design Process

Buildings can be certified as Passive with the help of a CPHC (Certified Passive House Consultant) via the Passive House Institute US (PHIUS) or Passive House Academy US (PHAUS). Both residential and commercial buildings utilize the Passive House model.

Passive Building: Principals

Passive building comprises a set of design principles used to attain a quantifiable and rigorous level of energy efficiency within a specific quantifiable comfort level. “Maximize your gains, minimize your losses” summarize the approach. To that end, a passive building is designed and built in accordance with these five building-science principles:

It employs continuous insulation through its entire envelope without any thermal bridging.
The building envelope is extremely airtight, preventing infiltration of outside air and loss of conditioned air.
It employs high-performance windows and doors
It uses some form of balanced heat- and moisture-recovery ventilation and uses a minimal space conditioning system.
Solar gain is managed to exploit the sun’s energy for heating purposes and to minimize it in cooling seasons.

Passive building principles can be applied to all building typologies, from single-family homes to apartment buildings to multi-story offices and skyscrapers.

The building for Cornell Tech’s new campus on New York’s Roosevelt Island by Handel Architects, will be the largest Passive Building in the world.

Passive Building Benefits

Passive buildings offer tremendous long -term benefits in addition to energy efficiency:

High levels of insulation and airtight construction provide unmatched comfort even in extreme conditions.
Continuous mechanical ventilation of fresh filtered air assures superb air quality.
A comprehensive systems approach to modeling, design and construction produces extremely resilient buildings.
Passive building is the best path to Net Zero and Net Positive buildings because it minimizes the load that renewable energy sources are required to provide. [3]

Click here to watch a 90-second video explaining the “Passive House”

[1] Waldsee BioHaus architect, Stephan Tanner

[2] “Passivhäuser im Bau bis zu 14% teurer”. Franz Alt. Retrieved 2009-06-05.

[3] www.phius.org/what-is-passive-building-/the-principles

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