What is a house of quality?
The house of quality is a matrix that answers one question: which technical characteristics of our design matter most to our customers? Developed in Japan in the 1970s as part of quality function deployment and popularised by Hauser and Clausing's 1988 article, it puts the voice of the customer and the voice of the engineer on one page, so that design priorities follow customer priorities rather than habit or the loudest opinion.
The rooms of the house
| Room | Content | Question it answers |
|---|---|---|
| Left wall | Customer needs (WHATs) and importance | What do customers want, and how much does it matter? |
| Ceiling | Technical characteristics (HOWs), direction ▲ ▼ ◆ | What can we measure and design? |
| Body | Relationship matrix ◎ 9, ○ 3, △ 1 | Which characteristics deliver which needs? |
| Roof | Correlations ++, +, −, −− | Where do characteristics help or fight each other? |
| Right wall | Customer ratings, goal, ratio, sales point, weight | Where are we behind competitors, and what will sell? |
| Basement | Technical importance, rank, targets, benchmarks | What should we prioritise, and what value should we aim for? |
House of quality example
A team designing a home blood pressure monitor lists six customer needs and eight technical characteristics, and compares the current model with two competing brands. "Readings I can trust" is the most important need and customers rate the current monitor only 3 of 5 against a goal of 5; with a strong sales point it takes 33.9% of the weight. "Measures quickly" and "Easy to keep and share my results" also carry weight (19.5% each): customers rate the current model 2 of 5 on both, behind Brand A.
The basement ranks measurement time (22.1%), measurement error (21.7%) and peak cuff pressure (18.4%) as the top technical priorities. The roof shows a strong negative correlation between the first two: measuring faster tends to make readings less accurate. That trade-off is the real design problem to solve, for example by measuring during inflation, rather than simply setting tight targets on both.
Tips
- Use real customer data for needs, importance and ratings: start with a voice of the customer study.
- Keep characteristics solution-free and measurable: "measurement time (s)", not "faster pump".
- Do not over-fill the matrix. If most cells have a symbol, the relationships are not discriminating.
- Every need needs a strong relationship; the tool flags needs with none.
- Carry the top characteristics into the next phases with quality function deployment.
How to use this House of Quality tool
- List the customer needs. Add the needs in the customer's words and rate their importance from 1 to 5.
- Add technical characteristics. Click + on the ceiling to add measurable characteristics, each with a unit, direction of improvement and target.
- Fill the relationship matrix. Click each cell to set a strong (9), medium (3) or weak (1) relationship.
- Complete the roof. Click the diamonds in the roof to mark positive and negative correlations between characteristics.
- Rate against competitors. In the planning table, enter customer ratings of your product and competitors, your goal and the sales point.
- Read the priorities. The basement shows the technical importance and rank of each characteristic; the insights flag trade-offs and gaps.
Frequently asked questions
What is a house of quality?
The house of quality is the first and best-known matrix of quality function deployment (QFD). It relates customer needs (the WHATs) to technical characteristics (the HOWs), weights them by importance and competitive position, and calculates which technical characteristics matter most. Its shape, with a triangular roof of correlations, gives it the name.
What are the rooms of the house of quality?
The left wall lists customer needs and their importance. The ceiling holds the technical characteristics and their direction of improvement. The body is the relationship matrix (9-3-1). The roof shows how characteristics affect each other. The right wall is the planning matrix with customer ratings of your product and competitors, goals and sales points. The basement holds technical importance, targets and technical benchmarks.
How is technical importance calculated?
First each customer need gets a weight: importance × improvement ratio (goal ÷ our current rating) × sales point, normalised to 100%. Then for each technical characteristic, multiply each need's weight by the relationship strength (9, 3 or 1) and add them up. The characteristics with the highest totals deserve the most design attention.
What does the roof show?
The roof (correlation matrix) shows how improving one technical characteristic affects another. Positive correlations (+, ++) help each other. Negative correlations (−, −−) are trade-offs: improving one makes the other worse. Trade-offs between high-priority characteristics are where design innovation is needed.
What is a sales point?
A sales point marks needs that can be used to sell the product: 1.5 for a strong selling point, 1.2 for a moderate one, 1.0 for none. It increases the weight of needs that will win customers, not just satisfy them.
What is the difference between the house of quality and QFD?
QFD is the whole method of deploying customer needs through design, parts, processes and production controls, typically in four phases. The house of quality is the first, most detailed phase: product planning. Use the quality function deployment tool for the full cascade.